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JOSIP JURAJ STROSMAYER UNIVERSITY FACULTY OF FOOD TECHNOLOGY OSIJEK Lidija Obad ENGLISH IN FOOD TECHNOLOGY II OSIJEK 2010. Izdavač Sveučilište Josipa Jurja Strossmayera u Osijeku Prehrambeno-tehnološki fakultet Osijek Recenzenti Dr.sc. Žaneta Ugarčić-Hardi red.prof. Prehrambeno-tehnološki fakultet, Osijek Dr.sc. Marija Omazić izv.prof. Filozofski fakultet, Osijek Lektura Emily Catherine Drača, prof. Tisak Grafika Osijek PREFACE This textbook is intended for the second year students of food technology. It is composed of 18 units which are closely connected with the field of study. The units are grouped into several sections covering the field of microbiology, biochemistry, science on nutrition, packaging and ecology. Furthermore, additional reading is provided giving the opportunity to extend some of the topics covered by the main units. Each unit starts with a pre-reading task aimed at activating students’ knowledge of the world they have already acquired and stimulating them for reading. In addition to that, various exercises for checking comprehension, either precede the text, giving a clear task and focus on essential information, or follow the text making the students refer to the text several times. Students use various reading strategies in fulfilling the prescribed tasks. They anticipate the content, read quickly to get the gist of the text or immerse in detailed reading, use graphs, diagrams, look for coherence and cohesion of the paragraphs or complete text. Vocabulary is checked through synonyms, antonyms, translations, collocations, word formation, and word families. Grammar is checked via sentence formation or in specific grammar tasks. Some exercises require of students active involvement in discussions and debates. At the end of the textbook there is an English- Croatian glossary providing very specific terminology and general English terms as well. Lidija Obad MA Contents Units 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. Page The World of Microbiology Microbes Structure and Function of Bacteria Viruses Using Microbes for Food Production Biochemistry Proteins Enzymes Carbohydrates Fats, Lipids and Oils Food Pyramids Functional Foods Nutrition, Brain Function and Behaviour Alter Your Mood with Food Chocolate: A Healthy Indulgence Genetically Modified Organisms Active and Intelligent Packaging Water Pollution and Society Glossary Additional reading References 1 6 9 14 18 22 26 31 35 39 44 50 56 62 67 72 77 84 90 95 115 UNIT 3 STRUCTURE AND FUNCTION OF BACTERIA Activity 1 Pre-reading task 1. How do bacteria affect the human body? 2. What are the possible shapes of bacteria? Activity 2 Text comprehension Read the text to answer these questions: 1. Why do bacteria cause diseases? 2. What are the known cell shapes of bacteria? 3. Why is cell arrangement important? 4. What are the important parts of cell structure? 5. What is the role of the cell membrane? Many of our most dreaded diseases are caused by bacteria, the most common group of prokaryotes. The structure and biological activities of bacteria enable them to infect and damage the body. Yet structures and functions unique to bacteria may be sensitive to antibiotics that inhibit or destroy essential properties of prokaryotic cells. As a result, many diseases that killed our ancestors are easily cured today. line 5 Bacterial structures are difficult or impossible to distinguish using light microscopy. The finer details of sub cellular structure are revealed best by high-resolution electron microscopy. The general shape of individual bacterial cells is usually discernible with the bright field microscope. Bacteria are differentiated into major categories based on microscopic observations. These groupings reflect morphological properties such as 1) cell shape, 2) cell size, 3) staining characteristics, 4) the manner in which similar cells are arranged. line 11 Cell shape and arrangement Most bacteria have a defined shape that falls into one of three morphological categories: 1) spherical cocci (singular coccus), 2) rod-shaped bacilli (singular bacillus), 3) spiral organisms. In addition, some bacteria are filamentous; they tend to form long strands composed of many cells. In these cases, an occasional cell may be seen after it breaks away from a longer filament. A few bacteria change their shapes and are called pleomorphic (pleo/mor; morph/form). line 18 A coccus is a spherical organism normally ranging between 0.4 and 2 um in diameter. Cocci generally appear in groups formed by the incomplete separation of cells during the reproductive process. The arrangement of the cells in the group is often indicative of an organism’s identity. Although cell arrangement can give some clue as to the identity of an organism, under certain conditions bacteria fail to grow in their characteristic patterns. line 23 Bacilli are rod-shaped organisms usually ranging between 1 and 10 um in length. Some are characteristically long and slender. Others are short and stumpy; they appear ovoid and are referred to as coccobacilli. Some bacilli are curved into a form resembling a comma. These cells are called vibrios, as in vibrio cholera, a pathogen that causes fatal gastrointestinal disease. Some bacteria are flat rectangular boxes with perfectly, straight edges. line 28 9 Spiral organisms are less common than cocci or bacilli and include the agent of syphilis. They are divided into two groups, spirilla and spirochetes. These two groups of microbes are very similar in shape but spirochetes are flexible whereas spirilla are rigid. line 31 Cell structure Although more than 1500 species of bacteria have been described, only about 100 are primarily human pathogens. The factors contributing to many biological activities, including their ability to initiate or promote disease, are often directly related to the exposed surface structures and appendages of the bacterial cell. line 36 In all cells cytoplasmic contents are separated from the environment by the cell membrane. In addition, almost all prokaryotic cells are surrounded by at least one other structure, the cell wall. In order to survive, the cell must remain separate from the environment. This separation is accomplished by the cell membrane. Major disruptions in this barrier result in the spilling of the cytoplasm from the cell and the death of the organism. line 41 The cell membrane in bacteria is a phospholipid-protein bilayer similar to that present in eykaryotic cells. The major difference is that there are no sterols in the cell membranes of most prokaryotes. The cell membrane is the site of many functions that are accomplished by specialized internal organelles in eukaryotes. These include: line 45 1. transport of molecules in and out of the cell; 2. secretion of extra cellular enzymes; 3. respiration and photosynthesis; 4. regulation of reproduction; 5. cell wall synthesis. line 50 Organisms must selectively regulate the transport of nutrients into and waste products out of the cell. Usually each type of molecule requires specific receptors that can recognize it and move it across the membrane. This is the function of many of the membrane proteins. The presence or absence of the corresponding receptor proteins in the cell membrane determines which molecules can be transported. line 55 Before they can be transported across the cell membrane, larger food molecules must be broken down outside the cell into smaller subunits. Such extra cellular digestion is mediated by enzymes released from the bacteria into their fluid environment. Secretion of extra cellular enzymes is another function of the cell membrane. line 59 The functions accomplished by eukaryotic mitochondria (energy generation) and chloroplasts (photosynthesis) are performed by the membrane in prokaryotes. The greater the membrane area in the cell, the more respiration and photosynthesis can occur. line 62 Production of bacterial progeny is partially regulated by the cell membrane. Specific proteins in the membrane attach to the replicating DNA and separate the duplicated chromosomes from each other. In addition, the cytoplasm of the daughter cells may be physically separated from each other by formation of a septum (cross wall). line 66 Molecules needed for constructing and repairing the cell wall are synthesized in the cytoplasm and transported outside the cell. Specialized membrane proteins transport these subunits across the cell membrane and assemble them into the growing cell wall. line 69 Adapted from various sources 10 Activity 3 Look at Figure 6 and explain the cell shapes and arrangements. Add further details by referring to the text. Figure 6. Cell shapes and arrangements whttp://www.zampwiki.com/?t=Bacillus_ (2009-12-13). Activity 4 Explain the cell structure according to Figure 7 and expand the explanation by referring to the text. Figure7. Cell structure www.macroevolution.net/prokaryotic.cell-structure.html(.2009-12-13). 11 Activity 5 Text comprehension Fill in the table using the information from the text. Cell type Size Shape 1-10 um Spherical Spiral Activity 6 Text comprehension Complete the sentences in the left-hand column with those in the right-hand column. 1. 2. 3. 4. 5. Cell membrane damage results in Molecule transport is done Extra cellular digestion is Molecules for cell wall reparation More respiration occurs a) are synthesized in the cytoplasm. b) the cell death. c) if the cell membrane is greater. d) mediated by enzymes. e) selectively. 1. ___ 2. ___ 3. ___ 4. ___ 5. ___ Activity 7 Vocabulary Give the singular form of the following nouns: Plural Singular Bacilli _____________ Cocci ______________ Bacteria ______________ Activity 8 Vocabulary Complete the following table: Noun Cell Verb to discern Disruption Secretion to attach to assemble 12 Adjective Activity 9 Vocabulary Complete the sentences using the words from activity 8 and make the necessary changes: 1. Heavy snow has _______________ the transport system in the city. 2. All students ____________________ in the meeting room. 3. We have observed the protein ____________________ to the DNA. 4. It was not easy to ________________ patterns in these figures. 5. The ________________ arrangement indicates the organism’s identity. 6. If the _________________ of gastric juices is increased it may cause problems. Activity 10 Grammar practice The past participle can be used in various roles: 1. as an adjective 2. as a part of compound tenses 3. as a part of passive voice 4. as a replacement for a relative clause, e.g. cocci appear in groups formed by separation ( instead ….. in groups which are formed by separation) Find three examples in the text for the following uses: 1. past participle as an adjective a)____________ b) ____________ c) _____________ 2. past participle in passives a)____________ b)_____________ c)______________ 3. past participle replacing a relative clause a)_______________________________________________________________ b)________________________________________________________________ c)________________________________________________________________ 13 UNIT 5 USING MICROBES FOR FOOD PRODUCTION Activity 1 Pre-reading task 1. How were microbes used in the past in food production? 2. How are they used today in the food industry? Activity 2 Read the text to answer these questions: 1 How long have people used microbes in food production? 2 What are the usual ways of using microbes in the food industry? 3. What is the condition for producing large quantities of by-products? 4. What food additives are produced from microbes and what is their effect on food? 5. Why are enzymes instrumental in food production? Since the dawn of history, people have been putting microbes to work. Processes discovered hundreds or thousands of years ago are still used today to produce bread, beer, wine, cheese etc. Moreover, recent developments in molecular biology are expanding the potential usefulness of microbes into new areas of industry, agriculture, medicine and food production. line 5 Microbes continue to be used in the food industry primarily in three ways. 1. Specific metabolic activities, usually fermentation reactions, generate organic compounds that accumulate and transform some edible substances into foods with more desirable characteristics. These altered properties usually help preserve foods and often enhance flavour, texture or digestibility. Dairy products, breads, soy sauce, pickled vegetables, alcoholic beverages and vinegar are produced by microbial fermentation. line 11 2. Microbial cells, cultivated in large quantities, are used as protein supplements in feed for livestock. Such single-cell proteins have also been suggested as alternative food resources for humans. line 13 3. Certain microbes produce metabolic by-products that have nutritional or flavour-enhancing properties when added to foods and feeds. Enzymes isolated from microorganisms are also instrumental in food production. line 16 Food additives Many vitamins, amino acids, nucleotides and enzymes that are commercially valuable to the food industry are obtained in high concentrations from microbial cultures. The microbes’ metabolic control mechanisms must be circumvented before large quantities of the desired byproduct can be synthesized and harvested. Thus, it is desirable to obtain microbes that have lost their sensitivity to metabolic regulation. For example, some mutants of Corynebacterium glutamicum can produce more than 200 times the amount of lysine required for growth. The amino acid extracted from these cultures is used for supplementing lysine-deficient plant proteins in many animal feeds. More than 300,000 tons of glutamic acid, another amino acid manufactured commercially by microbes, is used each year, primarily as the flavourenhancing salt, monosodium glutamate. Vitamin B12 is manufactured by commercial cultures of propionibacteria in amounts 50,000 times that required for its growth. Other microbial 18 produced vitamins include riboflavin and precursors of vitamin A and C. Microbes also produce huge quantities of nucleotides that have taste-enhancing properties. line 30 Many enzymes instrumental in food production are also derived from microbes. Amylases are used in the initial steps in several food fermentation processes to convert starch to fermentable sugars. They are also used to partially predigest foods for young children, to clarify fruit juices and in the manufacture of corn and chocolate syrups. The enzyme invertase, obtained from saccharomyces cerevisiae, prevents the crystallization of sugars by converting sucrose to the more soluble glucose and fructose. It is injected into some candies to liquefy the centers. Other fungal enzymes, pectinases, dissolve pectin, a naturally occurring thickening agent in ripe fruit. These enzymes are used to clarify juices and allow them to be concentrated without solidifying, and to remove the gummy material around coffee beans prior to roasting. Rennins are enzymes derived from moulds that are used to coagulate milk for cheese production. Not long ago, these curdling enzymes were obtained solely from the gastric juice of cattle and other animals. line 42 Adapted from various sources Figure 10 Microbes in food production http://www.jgi.doe.gov/News/LABfoods.jpg (2010-02-15) 19 Activity 3 Text comprehension Complete the sentences using the information from the text: 1. To obtain large quantities of by-products, it is important to ________________________. 2. Nucleotides are proved to have ________________________. 3. Microbial fermentation is used to produce _____________________________________. 4. Microbial produced vitamins include ________________________________________. Activity 4 Text comprehension Fill in the following table using the information from the text: Type of enzyme Usage Amylases Invertase curdling enzyme in cheese production thickening agent for juice clarification Activity 5 Text organization Put the following ideas in chronological order as they appear in the text: ______ condition for producing enzymes, vitamins, amino acids, in large quantities; ______ enzymes used in fruit juice production; ______ usage of microbes in the past ______ curdling agents used in the dairy industry; ______ usage of protein supplements in feed. Activity 6 Vocabulary Translate the following expressions and use them in your own sentences: a) flavour-enhancing properties __________________________ ___________________________________________________________________________ b) to circumvent control mechanism_____________________________ ___________________________________________________________________________ c) thickening agent_________________________ ___________________________________________________________________________ d) curdling enzymes__________________________ ___________________________________________________________________________ e) lysine-deficient plant____________________ ___________________________________________________________________________ 20 Activity 7 Vocabulary Complete the following table: Noun Verb preserve enhance convert liquefy solidify alter Adjective 21 UNIT 7 PROTEINS Activity 1 Pre-reading task 1. Why are proteins important for the human body? 2. What food is rich in proteins? Activity 2 Reading task Read the text to answer these questions: 1. How do proteins shape our life? 2. What are amino acids? 3. How are amino acids classified? 4. How are amino acids linked? 5. What is a helix? 6. What structure does collagen have? 7. What is a general belief about amino acids? 8. How can you define complete and incomplete protein food? When Dutch chemist Johann Mulder (1802-1880) first classified protein in 1838 as the prime substance of all life forms, he could scarcely guess how far-reaching his work would become. From Mulder's early grasp of what he was seeing, protein has become recognized as the essential life-substance of all living matter. In many ways, proteins act to shape our lives. They act as structural units to build our bodies. As enzymes they change our food into nutrients our cells can use. As antibodies, they shield us from disease. As peptide hormones, they send messages that coordinate continuous body activity. Proteins do much more: they guide our growth during childhood and then maintain our bodies throughout adulthood. line8 The story of protein must begin with its unique building materials, the amino acids. A major life-sustaining task of the human body is the constant building and rebuilding of all its body tissues. There are 22 amino acids, all of which are important in the body's metabolism. However, 10 of these 22 amino acids are designated as essential amino acids because the body cannot synthesize them in sufficient quantity or at all. The most recently (1992) declared essential amino acid is arginine named "molecule of the year" because it modulates the bioavailability of nitrous oxide (NO), a powerful vasodilator in the blood vessels that inhibits atherogenesis The remaining 12 amino acids are labeled "nonessential", as shown in Table 1. line 16 The building units, amino acids, are used by the body to construct specific tissue proteins. This process is made possible by the nature of amino acids, which enables them to form peptide linkages and arrange themselves into peptide chains. The dual nature of amino acids – the presence of a base (amino – NH2 ) group containing nitrogen on one end and an acid (carboxyl – COOH) group on the other – enables them to join in the characteristic chain structure of proteins. The end amino group of one amino acid joins the end carboxyl group of another amino acid beside it. This characteristic joining of specific amino acids in a specific sequence to make a specific protein is called a peptide bond. Long chains of amino acids linked in this manner form proteins and are called polypeptides. line 25 26 Table 1. Amino acids grouped as essential and nonessential Essential amino acids Arginine Histidine Isoleucine Leucine Lysine Methionine Phenylalanine Threonine Valine Nonessential amino acids Alanine Aspargine Aspartic acid Cystine (cysteine) Glutamic acid Glutamine Glycine Hydroxylysine Proline Serine Tyrosine To make a compact structure, the long polypeptide chains coil or fold back on themselves in a spiral shape called a helix. The proteins illustrate a huge diversity of compounds produced by specific amino acid linkages. As a result, according to their varied specific structures, tissue proteins perform many vital roles in body structure and metabolism. Here are some examples. Myosin, the fibrous protein present in muscle fiber and shown in Figure 12, is composed of 153 amino acid long chains that coil and unfold on contraction and relaxation. Shaped into long rods, these fibers end in two-headed bundles so that they can change their shape and bend, making it possible to tighten and contract muscles and relax them. Collagen, the structural protein, is made up of three separate polypeptide chains wound around each other to produce a triple helix. Thus strengthened, the collagen is shaped into long rods and bundled into stiff fibers because its job is to strengthen bone, cartilage, skin and other body structures to maintain their form. line 50 Figure 12. Myosine molecules www.colorado.edu...IPHY3430-200/010muscles.htm (2010-02-10) 27 There are many persons shopping for amino acids and taking them singly or as multiple supplements for a number of supposed improvements in health and fitness or as remedies for health problems. They buy tryptophan for insomnia, lysine arginine for herpes. Two groups of persons most vulnerable to such claims are athletes and elderly persons. The belief that protein is a major energy source and builds muscle strength leads to the use of amino acid supplements in an effort to attain this result. But carbohydrates and fats – not proteins – are fuel substrates in muscle tissue, and excess protein only places excess metabolic burden on the body. It is the exercise, not protein that increases and strengthens muscles. In the second group, older adults seek to avoid health problems or relieve the pain and stress of chronic illnesses of aging. The belief that amino acids will provide such magic elixirs is ill advised. They are both an expensive burden on the income and ineffective source of needed protein which is better found in an improved diet containing all the nutrients that work best together. line 65 A common way of designating the quality of protein foods is whether they are complete or incomplete in terms of the amounts of essential amino acids that they contain. Foods called complete protein foods are those that contain all the essential amino acids in sufficient quantity and ratio to meet the body's needs. These proteins are of animal origin: eggs, milk, cheese and meat including poultry and fish. Another protein of animal origin, gelatin, does not qualify because it lacks three essential amino acids- tryptophan, valine and isoleucine and has only small amounts of leucine. Incomplete protein foods are those deficient in one or more of the essential amino acids. These proteins are mostly of plant origin: grains, legumes, nuts, and seeds. In a mixed diet, however, animal and plant proteins complement one another. Even a mixture of plant proteins alone can provide adequate amounts of amino acids when our basic use of various grains is expanded to include soy protein and other dried legume (beans and peas) storage proteins. The value of variety in diets is therefore evident. line 77 Adapted from Essentials of Nutrition and Diet Therapy by Sue Rodwell Williams 28 Activity 3 Text comprehension Use the information from the text to complete these sentences: 1. Proteins are the prime substance of life because _________________________________ ________________________________________________. 2. The dual nature of amino acids enables them to _________________________________ _______________________________________. 3. Essential amino acids are those that___________________________________________ _____________________________________ . 4. Collagen is shaped into long rods and stiff fibers because ________________ ____________________________________________________________. 5. Fuel substrates in muscle tissue are _________________________. 6. Incomplete protein food is described as _______________________________________ _____________________________________________ . Activity 4 Text organization Order the following subtitles chronologically as they appear in the text: _____ Controversial attitudes towards amino acids _____ Protein functions _____ Types of protein food _____ Amino acid classification and structure Activity 5 Vocabulary Translate the following expressions and use them in your own sentences: a) life-sustaining task _________________________ ___________________________________________________________________________ b) excess metabolic burden _________________________ ___________________________________________________________________________ c) to relieve the pain_____________________________ ___________________________________________________________________________ d) two-headed bundles___________________________ ___________________________________________________________________________ Activity 6 Vocabulary Give the opposite meaning of the following expressions: chains coil protein excess muscle relaxation to sustain life ________________ ________________ ________________ _________________ 29 Activity 7 Sentence formation Use the following expressions to make sentences. 1.designated them amino acids essential are as the body cannot 10 because synthesize __________________________________________________________________ 2.childhood proteins is growth guided our by during ___________________________________________________________________________ 3.is amino acids a sequence of called the joining in a peptide bond ___________________________________________________________________________. 4.wrong the magic provide amino acids elixir a is that it completely belief ___________________________________________________________________________ Activity 8 Past Participle The past participle is often used to replace a relative clause e.g. Foods called complete protein foods…(instead of Foods which are called complete…). Find four examples in the text: 1. __________________________________________________________________ 2. __________________________________________________________________ 3. __________________________________________________________________ 4. __________________________________________________________________ 30 UNIT 8 ENZYMES Activity 1 Anticipation Skim the first sentence of each paragraph to anticipate the content of the text. Activity 2 Reading task Read the text to answer the questions: 1. 2. 3. 4. 5. 6. What is the relationship between enzymes and chemical reactions? What would happen to milk without enzymes? Why is every reaction in a cell catalyzed by a different enzyme? What is a co-enzyme? When is the function of co-enzymes impaired? How does environment influence enzymes? Enzymes, the key proteins in the cell, determine in large part all of the properties of the cell. They are responsible for the cell's ability to carry out its functions necessary for cell multiplication. Enzymes catalyze (speed up) the large number of chemical reactions in the cell. The conversion of one substance (the substrate) to another (the product) has been often measured at varying intervals. In the absence of an enzyme, the substrate, the substance on which the enzyme acts, is changed into a product so slowly that it is impossible to measure the product's formation. However, an enzyme can convert substrate into a product in a short time. For example, if milk is left at room temperature for several days, it sours as a result of the action of bacterial enzymes on the substrate, lactose, to form the final product, lactic acid. If the milk did not contain microorganisms that could break down lactose, the conversion of lactose to lactic acid (souring) would still occur, but it would take many thousands of years. A single enzyme molecule can convert as many as one million substrate molecules per second to products. Reactions between molecules can occur rapidly in the absence of enzymes if the temperature or pressure is raised to very high levels as can be accomplished in a chemical laboratory. However, life cannot exist under these conditions. Thus, enzymes take the place of heat and high pressure, allowing organisms to live at the relatively mild temperatures that exist on and beneath the surface of the earth. line 17 An enzyme functions first by combining, through weak bonding forces, with its substrate. This interaction places a stress on the chemical bonds in the substrate. The interaction places a stress on the chemical bonds in the substrate, which weakens them enough to break them and then forms new bonds. Enzymes act in two steps. First, the substrate binds to a specific portion of the enzyme, the active, or catalytic, site, to form an enzyme-substrate complex (Figure 13). Second, the products of the reaction are released; leaving the enzyme unchanged and free to combine with new substrate molecules. The arrangement of the enzyme and its substrate is commonly referred to as a "lock-and-key" arrangement; the substrate is the key and the enzyme the lock. Since the key must fit into the lock precisely, any particular enzyme will act on only one or a limited number of substrates, all of which must have a similar shape to fit the active site. This explains why almost every reaction in a cell is catalyzed by a different enzyme. As a result, hundreds of different enzymes exist in the cell, but relatively few molecules of each enzyme are needed, since they can be used over and over again. line 30 31 Many enzymes cannot function unless they have another molecule, a coenzyme, bound to them. Coenzymes are small nonprotein molecules such as nicotinamide adenine dinucleotide, abbreviated NAD, which is more than twice the size of a nucleotide. All enzymes have the same general function – to transfer molecules, atoms, or electrons from one molecule to another. In some cases, this molecule is transferred when the coenzyme is still bound to the enzyme; in other cases, the coenzyme separates from the enzyme in the transfer process. There are many different coenzymes but the same coenzyme can bind to different enzymes, so there fewer different coenzymes than there are enzymes. In some cases, the coenzyme is bound very tightly to the enzyme so that it is essentially a part of the enzyme as it carries out its function. In other cases, the coenzyme can readily separate from one enzyme and move to another enzyme. line 41 All coenzymes are synthesized from vitamins. If an organism lacks a vitamin, the functions of all the different enzymes whose activity requires that coenzyme are impaired. Thus, a single vitamin deficiency has serious consequences in animals. Besides, the enzymes are influenced by the environment, which affects how rapidly cells multiply. The features of the environment that are most important include temperature, pH, and salt concentration. Most enzymes function best at low salt concentrations and at pH values slightly above 7. In addition to being affected by extreme environmental conditions, the enzymes are inhibited by a variety of compounds. Some compounds inhibit in a reversible manner; others in an irreversible manner. Whether reversible or irreversible depends on whether the enzyme functions after the inhibitor is removed. In reversible inhibition, the inhibitor binds to but readily separates (dissociates) from the enzyme. In irreversible inhibition, the inhibitor binds very strongly to the enzyme and does not dissociate readily. In both types, attachment occurs to the active site of the enzyme, which prevents the substrate from binding to the site. line 54 Adapted from Microbiology, A Human Perspective by Nester, Roberts, Pearsall, Anderson Figure 13. Enzyme kinetics http://hillarybio.blogspot.com/2008_09_01_archive.html (2010-02-24) 32 Activity 3 Text comprehension Decide whether the following statements are true or false: 1. An enzyme takes a long time to convert substrate into a product. 2. The substrate binds to any part of the enzyme. 3. The substrate is the lock and the enzyme is the key. 4. Every reaction in a cell is catalyzed by a different enzyme. 5. The lack of vitamin impairs the functioning of enzymes. 6. Most enzymes function best at high salt concentrations. T T T T T T F F F F F F Activity 4 Text cohesion What is the role of the following connectors : however (line 7) thus (line 15) since (line 26) unless (31) as (line39) besides (line44) ____________________________________ ____________________________________ ____________________________________ ____________________________________ ____________________________________ ____________________________________ Activity 5 Points of reference What do the following words from the text refer to: They (line 2) refers to These conditions (line 15) refer to Its (line 18) refers to Them (line 19) refers to Others (line49) refer to ___________________________ ___________________________ __________________________ ___________________________ ___________________________ Activity 6 Vocabulary Match the words from the left-hand column with those from the right-hand column to make collocations: 1. bonding 2. catalytic 3. lock-and-key 4. transfer 5. vitamin a) arrangement b) process c) deficiency d) site e) forces 1 ___ 2 ___ 3 ___ 4 ___ 5 ___ 33 Activity 7 Sentence formation Use the collocations from activity 6 to make sentences: 1. _____________________________________________________________ 2. _____________________________________________________________ 3. _____________________________________________________________ 4. _____________________________________________________________ 5. _____________________________________________________________ Activity 8 Conditional clauses Complete these conditional clauses using the information from the text: 1. If your organism lacks a vitamin _____________________________________ . 2. Unless the enzymes had another molecule, a coenzyme , they __________________________. 3. If the milk had not contained microorganisms ___________________________. 4. If it were an irreversible inhibition, ____________________________________. 34 UNIT 11 FOOD PYRAMIDS Activity 1 Anticipate the content of the text by explaining the different food pyramids. Figures 19 & 20 Food Pyramids http://www.campshane.com/.../nutrition/pyramid.jpg (2010-02-24) http://bellani.files.wordpress.com/2009/01/mypyramid.jpg (2010-02-24) 44 Activity 2 Reading task Read the text to answer the following questions: 1. What was the purpose of the Basic Four? 2. What changes were introduced in the graphic of the late 1970s? 3. How was the message from the 1992 Food Pyramid formulated? 4. What are the differences between the eating patterns of the past and the present? 5. How does stress influence our digestion? 6. How does My Pyramid differ from the previous Food Pyramids? A Brief History of Dietary Recommendations First there was the "square meal", a four-cornered approach to meals that dated from 1943, when the U.S. Department of Agriculture (USDA) announced the Basic Four to help citizens achieve better nutrition during war shortages. The square meal included a meat portion, a vegetable or fruit portion, a starch portion, and a milk portion, three times a day every day. By the seventies Americans were no longer active and as they became fatter, scientists proved links between rich food and heart disease. It was obvious that the square meal needed an overhaul. line 7 In the late 1970s, the USDA added another category to the Basic Four and put the culpritssweets, alcohol and fat- into it. Despite, or perhaps because of, the fifth element, incidences of heart disease, diabetes, hypertension and stroke, and weight gain mounted. So during the eighties the USDA decided to get graphic. The agency came up with an emblem designed to signify what previous polygons could not – variety, proportion and moderation. The 1992 Food Pyramid stacked the food groups according to the proportions in which they should be consumed, with grains occupying the wider base and sweets at the top. The message was, and still is, make cereals, rice, pasta and bread the foundation of your diet. Consume plenty of vegetables and fruits. Enjoy milk, cheese, yogurt, and other dairy products. Eat some meat fish, poultry and legumes. Add a smattering of sweets, oils and fats. Unfortunately, the food pyramid did not make U.S. citizens healthier. Today, two-thirds of Americans over the age of twenty are overweight, and nearly one-third of adults are obese, according to the 1999-2000 National Health and Nutrition Examination. line 20 Increasingly poor nutritional habits and lack of exercise undermined the Food Pyramid's good intentions. The pattern of weight gain continued. Our bodies reflect what we put into them, what we do, and where and how we live. Before the mass commercialization of food products, people lived and ate closer to food sources. They ate whole foods. Today, there is the drive to fill commercial demand at the least possible cost and increase shelf life and visual appeal, whereas the quality of food deteriorates. Even though great advances have occurred in food cultivation, food suppliers are delivering foods that were raised far from most people's lives and often harvested weeks and months in advance of being sold. Lettuce harvested last week does not supply as many nutrients as that picked today. Besides, the Food and Drug Administration (FDA) approves irradiation of meat and poultry, fresh fruits and vegetables to decrease or eliminate harmful bacteria. Irradiation reduces spoilage bacteria and inhibits sprouting of vegetables and delays ripening. For example, irradiated strawberries stay unspoiled up to three weeks, versus three to five days for untreated berries. Thereby, nutritional value is decreased and food irradiation masks what may be unsanitary conditions in food processing plants. line 35 45 At the same time civilization is increasingly busy and food consumption patterns are being transformed – and not necessarily in good direction. Many families rely on packaged and processed food, heat-and-eat food, fast food. Even when we do eat at home, we tend to eat prepared or partially prepared food. Only about a third of home-cooked meals are made from scratch. As a result we are getting fewer nutrients, while our body remains genetically programmed to thrive on the whole foods of our ancestors. As we live in very stressful times, every time we are worried, sad or mad, our body reacts chemically. Like pollution, anxiety destabilizes our systems by creating free radicals. Stress uses up extra nutrients and makes existing nutrients more difficult to assimilate. In addition, stress often leads to overeating- and overeating the wrong foods. Anxious people do not reach for carrots; they reach for chocolate, chips and alcohol. Meanwhile, people are becoming more inert and less physically active. line 46 Since consumers did not follow the advice of the old Food Pyramid, The USDA went to work, with the goal of incorporating the latest science and making not a diet, but a set of nutritional and educational tools. They aimed at a "food guidance system", that should be much more motivating than the old food pyramid. The result , My Pyramid, is the tools designed to encourage behavioral changes. While the old pyramid guided everybody to eat the same proportion of fruits or vegetables, My Pyramid has a more personalized approach. line52 For a quick estimate of what and how much you need to eat, you can simply enter your age, sex and activity level in the My Pyramid Plan Box on the website. A page immediately pops up telling you how many servings of each group you need to eat daily. The website shows six coloured food-group segments: orange for grains, green for vegetables, red for fruit, yellow for healthful oils, blue for milk, and purple for lean meat, poultry, seafood, beans and eggs. Clicking on each one directs you into that specific food group and presents a cornucopia of information on why each food group is vitally important to your health and weight. Finally, the new stairway image on the pyramid reminds users to be more active, and a few clicks on physical activity will show you how many calories various activities burn, and so you learn the health benefits of exercise. line 62 Adapted from What Should I Eat? A Complete Guide to the New Food Pyramid by Tershia d' Elgin 46 Activity 3 Text organization Skim the text to order these subtitles chronologically as they appear in the text: ______ My pyramid _______ Eating patterns of the past and the present _______ Present changes of food consumption patterns _______ Historical overview of diet guidelines Activity 4 Text comprehension Fill in the following sentences using the information from the text: 1. In the 1990s the Food Pyramid advised citizens to eat ________________________ ____________________________________________________________________. 2. Although the shelf life of products has increased today, food quality has deteriorated because ______________________________________________________________ 3. Irradiation is used today to ____________________________________________. 4. The present food consumption patterns have changed and people eat ____________________________________________________________________ 5. Stress destabilizes our body because ____________________________________ ________________________________________________________________. Activity 5 Vocabulary Find words in the text that mean the same as: - economical use ___________________________ - food leftovers ___________________________ - satisfying meal ___________________________ - quality decline ___________________________ - revision or thorough examination ___________________________ - to arrange or pile up ___________________________ - a small scattered number or amount __________________________ - abundance ___________________________ - visual attraction ___________________________ - to produce an emblem ___________________________ 47 Activity 6 Vocabulary Translate the following expressions and use them in your own sentences: a) to eat in moderation _________________________ __________________________________________________________________. b) to undermine good intentions______________________ ____________________________________________________________________. c) sprouting of vegetables __________________________ ____________________________________________________________________. d) to delay fruit ripening __________________________ ___________________________________________________________________. Activity 7 Vocabulary Analyze the Eating Pyramid in Figure 21 and fill in the missing words in the paragraph below based on the information offered in the pyramid. The list of the missing words contains more words than needed: insulin, nutrition, falling, grains, health, quality, carbohydrates, exercise, pyramid, processed, developed. The Healthy Eating Pyramid created by the __________ experts from the Harvard School of Public Health is based on the best available scientific evidence about the links between diet and ________. This new pyramid fixes fundamental flaws in the USDA ________ and gives useful information to help people make better choices regarding their diet. This pyramid sits on a foundation of daily __________ and weight control. The other bricks of the pyramid include whole ___________ such as whole-wheat bread and brown rice which are digested slowly, give energy and prevent type 2 diabetes. Whole grains are an excellent source of _________________ mainly needed for energy. The body can't digest whole grains as quickly as it can highly _________________ carbohydrates. This keeps blood sugar and insulin levels from rising, then ________________ too quickly. Control of blood sugar and _____________ can keep hunger at bay and may prevent the development of type 2 diabetes. 48 Activity 8 Compare the Food Pyramid in Figure 19 with the Harvard Pyramid in Figure 21 and list several differences and similarities: Similarities 1. 2. 3. 4. 5. Differences ________________________________ 1. ________________________________ ________________________________ 2. ________________________________ ________________________________ 3._________________________________ _________________________________4. ________________________________ ________________________________ 5. ________________________________ Figure 21 The Healthy Harvard Pyramid http://www.hsph.harvard.edu/nutritionsource/images/H.(2010-02-24) Activity 9. Read the following paragraph and pose four questions to cover the essential information. Give a suitable title to the paragraph. The Healthy Eating Pyramid puts some fats near the base, indicating they are okay to eat. Although this recommendation seems to go against conventional wisdom, it is exactly in line with the evidence and with common eating habits. The average American gets one-third or more of his or her daily calories from fats, so placing them near the foundation of the pyramid makes sense. Note, though, that it specifically mentions healthy fats and oils, not all types of fats. Good sources of healthy unsaturated fats include olive, canola, soy, corn, sunflower and other vegetable oils, trans-fat free margarines, nuts seeds and fatty fish such as salmon. 49 UNIT 12 FUNCTIONAL FOODS Activity 1 Anticipation Skim the first sentence of each paragraph and try to give the definition of functional food. Activity 2 Reading task Read the text to answer the following questions: 1.Why is functional food important in our diet? 2. How do consumers react to functional food? 3. What is found in whole foods? 4. What effect does dietary fiber have on human health? 5. Are phytosterols good for health? Why? Functional foods are any foods, modified foods, or food ingredients that provide structural, functional, or health benefits, promoting optimal health, longevity and quality of life. In short, functional foods are food products that provide specific health benefits beyond the traditional nutrients they contain. Terms used to describe functional foods include fitness, hypernutritional, super foods, as well as foodiceuticals and nutraceuticals. line 5 The reason driving consumer interest in functional food includes increasing stamina and vigor to meet the stresses of modern lifestyles, offsetting unhealthy diet habits, body weight control ( nearly 50% of the population in many industrialized countries is overweight), prevention of degenerative diseases (heart disease, stroke, cancer), counteracting the effects of lack of exercise, and maintaining youthfulness. Market studies provide evidence consumers are increasingly aware of and knowledgeable about foods and ingredients and their health benefits. The market potential in the USA for functional foods grew from $11 to $ 20.5 billion between 1995 and 2001 with an annual growth rate of 10.9%. line 13 The concept of whole foods should be emphasized rather than fortification of less nutritious foods with purified functional compounds, because whole grains and minimally processed fruits and vegetables are often a better source of functional ingredients and are generally multifunctional. In addition, whole foods may contain several functional ingredients, as well as health-promoting components, that have not yet been identified. In line with the concept that whole foods provide more benefits, many nutritionists believe that the base of the USDA Food Guide Pyramid should include 6-11 servings of foods from whole grain products, rather than listing breads, cereals, rice and pastas – all foods from grains that may be from whole- or refined-grain fractions. line 22 The functional ingredients discussed in this overview emphasize that cereal grains, fruits, vegetables and other edible plant parts should be included in our daily diets. Cereal products will play a major role in the development and marketing of functional foods. In addition, cereals can be a source of ingredients with added health benefits, and cereal products can serve as a vehicle for delivering functional ingredients from other sources. line 27 50 Functional compounds Dietary Fiber Dietary fiber produces a feeling of satiety and provides chewing resistance. It also contributes to increased volume of consumed food. Cereal grains and grain properties of cereal fibers have been extensively investigated. Cereal fractions with reported health benefits resulting from the lowering of cholesterol and triglycerides include oat products (bran, rolled oats), rice products (bran, bran oil), barley products and corn fiber oil. line 34 Fructooligosaccharides Wheat, barley, rye, garlic onion, chicory, leek, artichoke and banana are all sources of fructooligosaccharides. They belong to a class of compounds that includes fructans and inulin. Fructooligosaccharides have been reported to reduce serum cholesterol, blood pressure, toxic metabolites, prevent cancer, constipation, diarrhea and improve liver function. line 39 Carotenoids More than 600 carotenoids have been identified in various plants. Carotenoids are red, orange and yellow pigments found in plant and algal sources. The most abundant carotenoid is ß-carotene. As antioxidants, carotenoids react with free radicals, protective against degenerative diseases (cancer, atherosclerosis) and premature aging. line 44 Phytosterols Sources of phytosterols include wheat germ oil, corn oil, corn, rice, bran, buckwheat, sesame seed, coconut oil, and almonds. Phytosterols have been reported to reduce colon cancer, decrease cholesterol absorption, lower LDL levels and reduce incidence of gallstones. Flavonoids More than 4000 flavonoids have been identified. Onion, broccoli, red wine and tea are good sources of many flavonoids; unprocessed or minimally processed fresh ingredients and foods provide more benefits from flavonoids than processed products. Green tea contains nearly 70 mg of the flavonoids and has been shown to reduce the risk of gastric, esophageal and colon cancer. Flavonoids found in soybean and soybean products (tofu, soy milk and flour) have antibacterial and antifungal activity. line55 Adapted from various sources Figure 22. Functional food http://www.aat-taa.eu/images/research/products.jpg (2010-02-24) 51 Figure 23. Functional food http://www.purepossibilities.com/images/liquid_vitamins/ViBE_fruit_vegetables.jpg (2010-03-12) Activity 3 List some advantages and disadvantages of functional and whole food. Advantages of whole food Disadvantages a) ________________________ a) _______________________________ b) ________________________ b) _______________________________ c) ________________________ c) _______________________________ 52 Advantages of functional food Disadvantages a) _________________________ a) ______________________________ b) _________________________ b) ______________________________ c)__________________________ c) ______________________________ Activity 4 Text comprehension Fill in the following table: Type of functional compound Dietary fibre Source Benefit corn oil, almonds broccoli, red wine rye, barley wheat Carotenoids Activity 5 Vocabulary Translate the following expressions and use them in your own sentences: a) nutraceuticals _________________________ ________________________________________________________________. b) stamina and vigor ______________________ ________________________________________________________________: c) to offset diet habits ____________________ ________________________________________________________________. d) food fortification ______________________ ________________________________________________________________. e) feeling of satiety ______________________ ________________________________________________________________. f) barley and oat products _________________ ________________________________________________________________. 53 Activity 6 Scan the following table and underline functional components which reduce the risk of cardiovascular diseases: Figure 24. Functional food components Examples of Functional Food Components Functional components Source Potential benefits Source: International Food Information Council Carotenoids Alpha-carotene/Beta-carotene Carrots, Fruits, Vegetables Neutralize free radicals, which may cause damage to cells Lutein Green vegetables Reduce the risk of macular degeneration Lycopene Tomato products (ketchup, sauces) Reduce the risk of prostate cancer Dietary Fibre Insoluble Fibre Wheat Bran Reduce risk of breast or colon cancer Beta-Glucan Oats, barley Reduce risk of cardiovascular disease. Protect against heart disease and some cancers; lower LDL and total cholesterol Soluble Fibre Psyllium Reduce risk of cardiovascular disease. Protect against heart disease and some cancers; lower LDL and total cholesterol Fatty Acids Long chain omega-3 Fatty Acids-DHA/EPA Salmon and other fish oils Reduce risk of cardiovascular disease. Improve mental, visual functions Conjugated Linoleic Acid (CLA) Cheese, meat products Improve body composition. Decrease risk of certain cancers Anthocyanidins Fruits Neutralize free radicals; reduce risk of cancer Catechins Tea Neutralize free radicals; reduce risk of cancer Flavonones Citrus Neutralize free radicals; reduce risk of cancer Flavones Fruits/vegetables Neutralize free radicals; reduce risk of cancer Lignans Flax, rye, vegetables Prevention of cancer, renal failure Tannins (proanthocyanidines) Cranberries, cranberry products, cocoa, chocolate Improve urinary tract health. Reduce risk of cardiovascular disease Phenolics Plant Sterols Stanol ester Corn, soy, wheat, wood oils Lower blood cholesterol levels by inhibiting cholesterol absorption Prebiotics/Probiotics Fructo-oligosaccharides (FOS) Jerusalem artichokes, shallots, onion powder Improve quality of intestinal microflora; gastrointestinal health Lactobacillus Yogurt, Other dairy Improve quality of intestinal microflora; gastrointestinal health Soy Phytoestrogens Isoflavones: Daidzein Genistein Soybeans and soy-based foods Menopause symptoms, such as hot flashes protect against heart disease and some cancers; lower LDL and total cholesterol http://www.4agr.gc.ca/AAFC-AAc/display-afficher.do(2010-02-22) 54 Activity 7 Vocabulary Use each of these words to make a sentence. NUTRIENT NUTRITIONIST NUTRITION NUTRITION NUTRITIOUS NUTRITIVE 1. _____________________________________________________________________. 2. _____________________________________________________________________. 3. _____________________________________________________________________. 4. _____________________________________________________________________. 5. _____________________________________________________________________. Activity 8 Vocabulary Complete the following table: Noun Verb Adjective fortification modified Emphasize Knowledge Deliver Activity 9 Vocabulary Complete the sentences using the words from activity 8 and make necessary changes: 1. 2. 3. 4. 5. I’d like to _____________ the importance of learning foreign languages. This fruit drink is ______________ with vitamin C. We usually get two _________________ of mail every day. The proposals were unpopular and were accepted in a ____________ form. He is very _______________ about English literature. 55 UNIT 16 GENETICALLY MODIFIED ORGANISMS Activity 1 Pre-reading task 1. Is GM food our future? 2. What are the advantages or disadvantages of GM? 3. Would you accept GM food? Why? Figure 29 http://www.repairstemcell.files.wordpress.com/2009/03/ge (2010-03-05) By far the most common genetically modified (GM) organisms are crop plants. But the technology has now been applied to almost all forms of life, from pets that glow under UV light to bacteria which form HIV blocking “living condoms” and from pigs bearing spinach genes to goats that produce spider silk. line 4 GM tomatoes, as puree, first appeared on British supermarket shelves in 1996 (a different fresh GM tomato first appeared in the US in 1994), but the consumer furor that surrounded GM technology did not erupt until February 1999. This was because a controversial study suggested that a few strains of GM potatoes might be toxic to laboratory rats. Those experiments, subsequently criticized by other experts, were carried out in Scotland. line 9 What followed was a European anti-GM food campaign of near religious fervour. Spearheaded in the UK by environmental groups and some newspapers, the campaign would have far-reaching consequences. It culminated in an unofficial moratorium on the growth and 72 import of GM crops in Europe and led to a trade dispute with the US. GM crops are very rare in Europe, strict labeling laws and regulations are in place for food and public opinion towards the technology remains largely negative. GM produce has been taken up with far less fuss in the US (where it does not have to be labeled), in Canada, China, Argentina, Australia and elsewhere. line 17 The human race has methodically improved crop plants through selective breeding for many thousands of years, but genetic engineering allows that time-consuming process to be accelerated and exotic traits from unrelated species to be introduced. But not everyone agrees that it represents progress. The root of genetic engineering in crops lies in the 1997 discovery that soil bug Agrobacterium tumefaciens can be used as a tool to inject potentially useful genes into plants. With the help of that microbe and other gene-implantation technologies , geneticists have developed new crop types. line 24 Most of these are modified to be pest, disease or herbicide resistant and include: soya, wheat, oilseed rape (canola), cotton, sugar beet, walnuts, potatoes, peanuts, tomatoes, lettuce, onion etc. The bacterial gene Bt is one of the most commonly inserted. It produces an insecticidal toxin that is harmless to people. Supporters of GM technology argue that engineered crops – such as vitamin A-boosted golden rice or protein-enhanced potatoes – can improve nutrition, that drought- or salt-resistant varieties can flourish in poor conditions and stave off world hunger and that insect-repelling crops protect the environment by minimizing pesticide use. Other plants have been engineered to improve flavour, increase shelf-life, increase hardiness and to be allergen-free. Geneticists have even created a no-tears onion to banish culinary crying and novel caffeine-free plants. line 33 Critics fear that what they call “Frankenstein foods” could have unforeseen adverse heart effects on consumers producing toxic proteins (and allergens) or transferring antibiotic resistance and other genes to human-gut bacteria to damaging effect. But there has been little evidence to back up such risks so far. More plausible threats are that modified crops could become insidious super weeds or that they could accidentally breed with wild plants or other crops- genetically polluting the environment. This could be a potentially serious problem if “pharm” crops, engineered to produce pharmaceutical drugs accidentally breed with food varieties (or seeds become mixed up). Large numbers of field trials, carried out by the UK government and others, reveal that gene transfer occurs. One 2002 study showed that transgenes had spread from US to traditional maize varieties in Mexico. Studies also proved that that pollen from FM plants can be carried on the wind for tens of kilometers. Many experts agree that insect-repelling plants will also speed the evolution of insecticide-resistant crops. Environmentalists also argue that growing GM crops affects farmland biodiversity. Pickrell,John. Instant Expert GM Organisms, New Scientist, 2006. http://www.newscientist.com/channel/life/gm-food/dn9921 73 Activity 2 Text comprehension Decide if the following statements are true or false. 1. European attitude towards GM crops is mainly negative. 2. Sugar beet and walnuts are also genetically modified. 3. Gm crops are not popular in Australia and Argentina. 4. GM supporters claim that GM plants are good for environment. 5. Gene transfer from GM plants to wild plants can occur. TF TF TF TF TF Activity 3 Text comprehension Complete the sentences using information from the text: 1. The negative attitude towards GM technology erupted in the USA in 1999 because _______________________________________________________________. 2. Genetic engineering can accelerate ________________________________ _______________________________________________________________. 3. New crop types were developed due to _____________________________ _______________________________________________________________. 4. Our nutrition could be improved by new plant varieties like ____________ ________________________________________________________________ 5. GM food could have unpredicted effects on humans such as ____________ _______________________________________________________________. Activity 4 Vocabulary Translate the following expressions and use them in your own sentences: 1. to take up produce ____________________ _______________________________________________________________. 2. gene-implantation technology ______________________ _______________________________________________________________. 3. pest-resistant plant _____________________ _______________________________________________________________. 74 4. plant breeding ___________________ _______________________________________________________________. 5. to stave off world hunger _____________________ _______________________________________________________________. 6. vitamin A-boosted rice ____________________ _______________________________________________________________. 7. field trials ____________________ _______________________________________________________________. 8. insect-repelling crop ___________________ _______________________________________________________________. Activity 5 Vocabulary Use each of these words to make sentences. GENETICS GENETICIST GENE GENETICAL 1. ___________________________________________________________________. 2. ___________________________________________________________________. 3. ___________________________________________________________________. 4. ___________________________________________________________________. 75 Activity 6 Vocabulary Match the words on the left side with those on the right side to make collocations: 1. selective 2. gene 3. genetic 4. no-tears 5. adverse 6. human-gut 7. herbicide a) engineering b) effect c) bacteria d) resistant e) transfer f) breeding g) onion Activity 7 Put the sentences in the correct order to make a coherent paragraph. _____ These “superweeds” would then be herbicide tolerant as well. _____ The possibility of interbreeding is shown by the defense of farmers against lawsuits filed by Monsanto. _____ Other introduced genes may cross over into non-modified crops planted next to GM crops. _____ The company has filed patent infringement lawsuits against farmers who may have harvested GM crops. ______ Another concern is that crop plants engineered for herbicide tolerance and weeds will cross-breed, resulting in the transfer of the herbicide resistance genes from the crops into the weeds. ______ Monsanto claims that the farmers obtained Monsanto-licensed GM seeds from an unknown source and did not pay royalties to Monsanto. Activity 8 Put the following words in the correct order to make sentences. 1. GM Europe was crops in import the stopped of. ____________________________________________________________. 2. were plants shelf-life and improve many flavour engineered to. _____________________________________________________________. 3. could crops plants environment modified breed other in accidentally with the _____________________________________________________________. 76 UNIT 18 WATER POLLUTION AND SOCIETY Activity 1 Pre-reading task 1. How can water be polluted? 2. What are the results of pollution? 3. What can we do to prevent further pollution? Activity 2 Reading task Read the text to answer these questions: 1. 2. 3. 4. 5. How is the growth of aquatic plants and algae stimulated? What is eutrophication? When is fish respiration impaired? How do chemical pollutants enter waterways? Why is an excessive growth of algae dangerous? WATER POLLUTION AND SOCIETY By David Krantz and Brad Kifferstein Figure 32 Water on Earth http://www.umich.edu/~gs265/society/waterpollution.htm (2010-03-07) Introduction Comprising over 70% of the Earth's surface, water is undoubtedly the most precious natural resource that exists on our planet. Without the seemingly invaluable compound comprised of hydrogen and oxygen, life on Earth would be non-existent: it is essential for everything on our planet to grow and prosper. Although we as humans recognize this fact, we disregard it by 84 polluting our rivers, lakes, and oceans. Subsequently, we are slowly but surely harming our planet to the point where organisms are dying at a very alarming rate. In addition to innocent organisms dying off, our drinking water has become greatly affected as is our ability to use water for recreational purposes. In order to combat water pollution, we must understand the problems and become part of the solution. line 9 Causes of Pollution Many causes of pollution including sewage and fertilizers contain nutrients such as nitrates phosphates. In excess levels, nutrients over stimulate the growth of aquatic plants and algae. Excessive growth of these types of organisms consequently clogs our waterways, use up dissolved oxygen as they decompose, and block light to deeper waters. This, in turn, proves harmful to aquatic organisms as it affects the respiration ability of fish and other invertebrates that reside in water. line 15 Pollution is also caused when silt and other suspended solids, such as soil, wash off ploughed fields, construction and logging sites, urban areas and eroded river banks when it rains. Under natural conditions, lakes, rivers, and other water bodies undergo Eutrophication, an aging process that slowly fills in the water body with sediment and organic matter. When these sediments enter various bodies of water, fish respiration becomes impaired, plant productivity and water depth become reduced, and aquatic organisms and their environments become suffocated. Pollution in the form of organic material enters waterways in many different forms as sewage, as leaves and grass clippings, or as runoff from livestock feedlots and pastures. When natural bacteria and protozoan in the water break down this organic material, they begin to use up the oxygen dissolved in the water. Many types of fish and bottom-dwelling animals cannot survive when levels of dissolved oxygen drop below two to five parts per million. When this occurs, it kills aquatic organisms in large numbers which leads to disruptions in the food chain. line Figure 33. Polluted river http://www.umich.edu/~gs265/society/waterpollution.htm (2010-03-07) 85 Polluted Rivers in the United Kingdom The pollution of rivers and streams with chemical contaminants has become one of the most crucial environmental problems within the 20th century. Waterborne chemical pollution entering rivers and streams cause tremendous amounts of destruction. Pathogens are another type of pollution that proves very harmful. They can cause many illnesses that range from typhoid and dysentery to minor respiratory and skin diseases. Pathogens include such organisms as bacteria, viruses, and protozoan. These pollutants enter waterways through untreated sewage, storm drains, septic tanks, runoff from farms, and particularly boats that dump sewage. Though microscopic, these pollutants have a tremendous effect evidenced by their ability to cause sickness. Krantz,David;Kifferstein,Brad. Water Pollution and Society, 2010. http://www.umich.edu/~gs265/society/waterpollution.htm (2010-03-07) 86 Activity 3 Text comprehension Match the beginnings and endings of the sentences. 1. Life on Earth would not exist if a) various dangerous diseases. 2. As humans pollute rivers and oceans b) aquatic organisms will die. 3. An enormous growth of algae can c) there were no hydrogen and oxygen. 4. If the level of dissolved oxygen drops d) refers to chemical contamination of rivers. 5. One of the key problems e) our drinking water becomes greatly affected. 6. Pathogens as pollutants cause f) clog the waterways 1 _____ 2 _____ 3 _____ 4______ 5_____ 6 _____ Activity 4 Vocabulary Translate the following expressions and use them in your own sentences. 1. to clog waterways ______________________ _________________________________________________________________. 2. to wash off ploughed fields ______________________ _________________________________________________________________. 3. construction and logging site ______________________ _________________________________________________________________. 4. to suffocate aquatic organisms ______________________ __________________________________________________________________. 5. runoff from feedlots ______________________ __________________________________________________________________. 6. disruption of food chain ______________________ _________________________________________________________________. Activity 5 Vocabulary Complete the following table: Noun Verb Prosper Suffocate Adjective Contaminant Drain Reside 87 Activity 6 Vocabulary Fill in the gaps with the words from exercise 5 and make necessary changes: 1. 2. 3. 4. His family now _______________ in the south of France. The report said that the victims ______________ in the fumes. A country’s future _______________ depends upon the quality of education. We ___________ the pond and filled it with fresh water. Activity 7 Read the text and pose five questions covering essential information. ADDITIONAL FORMS OF WATER POLLUTION Three last forms of water pollution exist in the forms of petroleum, radioactive substances, and heat. Petroleum often pollutes water bodies in the form of oil, resulting from oil spills. The previously mentioned Exxon Valdez is an example of this type of water pollution. These large-scale accidental discharges of petroleum are an important cause of pollution along shore lines. Besides the super tankers, off-shore drilling operations contribute a large share of pollution. One estimate is that one ton of oil is spilled for every million tons of oil transported. This is equal to about 0.0001 percent. Radioactive substances are produced in the form of waste from nuclear power plants, and from the industrial, medical, and scientific use of radioactive materials. Specific forms of waste are uranium and thorium mining and refining. The last form of water pollution is heat. Heat is a pollutant because increased temperatures result in the deaths of many aquatic organisms. These decreases in temperatures are caused when a discharge of cooling water by factories and power plants occurs. 1._________________________________________________________________________? 2._________________________________________________________________________? 3._________________________________________________________________________? 4._________________________________________________________________________? 5._________________________________________________________________________? 88 Activity 8 Read the text and complete with these words: impact, spread, coastal, drilling, coral, demonstrators. Figure 34. Greenpeace movement http://www.umich.edu/~gs265/society/waterpollution.htm (2010-03-07) Demonstrators Protest Drilling Oil pollution is a growing problem, particularly devastating to_________ wildlife. Small quantities of oil ____________ rapidly across long distances to form deadly oil slicks. In this picture, ______________ with "oil-covered" plastic animals protest a potential________ project in Key Largo, Florida. Whether or not accidental spills occur during the project, its ____________ on the delicate marine ecosystem of the __________ reefs could be devastating. Activity 9 Put these sentences in the correct order to make a coherent paragraph. Oil Spill Clean-up _____ Even small amounts spread rapidly across large areas of water. _____ Tanker spills are an increasing environmental problem because once oil has spilled, it is virtually impossible to completely remove or contain it. _____ Workers use special nets to clean up a California beach after an oil tanker spill _____ Attempts to chemically treat or sink the oil may further disrupt marine and beach ecosystems. ______ Because oil and water do not mix, the oil floats on the water and then washes up on broad expanses of shoreline. 89 ADDITIONAL READING UNIT 1 CLASSIFYING WATER POLLUTION The major sources of water pollution can be classified as municipal, industrial, and agricultural. Municipal water pollution consists of waste water from homes and commercial establishments. For many years, the main goal of treating municipal wastewater was simply to reduce its content of suspended solids, oxygen-demanding materials, dissolved inorganic compounds, and harmful bacteria. In recent years, however, more stress has been placed on improving means of disposal of the solid residues from the municipal treatment processes. The basic methods of treating municipal wastewater fall into three stages: primary treatment, including grit removal, screening, grinding, and sedimentation; secondary treatment, which entails oxidation of dissolved organic matter by means of using biologically active sludge, which is then filtered off; and tertiary treatment, in which advanced biological methods of nitrogen removal and chemical and physical methods such as granular filtration and activated carbon absorption are employed. The handling and disposal of solid residues can account for 25 to 50 percent of the capital and operational costs of a treatment plant. The characteristics of industrial waste waters can differ considerably both within and among industries. The impact of industrial discharges depends not only on their collective characteristics, such as biochemical oxygen demand and the amount of suspended solids, but also on their content of specific inorganic and organic substances. Three options are available in controlling industrial wastewater. Control can take place at the point of generation in the plant; wastewater can be pre-treated for discharge to municipal treatment sources; or wastewater can be treated completely at the plant and either reused or discharged directly into receiving waters. Wastewater Treatment Raw sewage includes waste from sinks, toilets, and industrial processes. Treatment of the sewage is required before it can be safely buried, used, or released back into local water systems. In a treatment plant, the waste is passed through a series of screens, chambers, and chemical processes to reduce its bulk and toxicity. The three general phases of treatment are primary, secondary, and tertiary. During primary treatment, a large percentage of the suspended solids and inorganic material is removed from the sewage. The focus of secondary treatment is reducing organic material by accelerating natural biological processes. Tertiary 95 treatment is necessary when the water will be reused; 99 percent of solids are removed and various chemical processes are used to ensure the water is as free from impurity as possible. Agriculture, including commercial livestock and poultry farming, is the source of many organic and inorganic pollutants in surface waters and groundwater. These contaminants include both sediment from erosion cropland and compounds of phosphorus and nitrogen that partly originate in animal wastes and commercial fertilizers. Animal wastes are high in oxygen demanding material, nitrogen and phosphorus, and they often harbour pathogenic organisms. Wastes from commercial feeders are contained and disposed of on land; their main threat to natural waters, therefore, is from runoff and leaching. Control may involve settling basins for liquids, limited biological treatment in aerobic or anaerobic lagoons, and a variety of other methods. Ground Water Ninety-five percent of all fresh water on earth is ground water. Ground water is found in natural rock formations. These formations, called aquifers, are a vital natural resource with many uses. Nationally, 53% of the population relies on ground water as a source of drinking water. In rural areas this figure is even higher. Eighty one percent of community water is dependent on ground water. Although the 1992 Section 305(b) State Water Quality Reports indicate that, overall, the Nation’s ground water quality is good to excellent, many local areas have experienced significant ground water contamination. Some examples are leaking underground storage tanks and municipal landfills. Legislation Several forms of legislation have been passed in recent decades to try to control water pollution. In 1970, the Clean Water Act provided 50 billion dollars to cities and states to build wastewater facilities. This has helped control surface water pollution from industrial and municipal sources throughout the United States. When congress passed the Clean Water Act in 1972, states were given primary authority to set their own standards for their water. In addition to these standards, the act required that all state beneficial uses and their criteria must comply with the “fishable and swimmable” goals of the act. This essentially means that state beneficial uses must be able to support aquatic life and recreational use. Because it is impossible to test water for every type of disease-causing organism, states usually look to identify indicator bacteria. One for example is a bacteria known as faecal coliforms. Figure 1 shows the quality of water for each every state in the United States, click on the US link). These indicator bacteria suggest that a certain selection of water may be contaminated with untreated sewage and that other, more dangerous, organisms are present. These legislations are an important part in the fight against water pollution. They are useful in preventing Environmental catastrophes. The graph shows reported pollution incidents since 1989-1994. If stronger legislations existed, perhaps these events would never have occurred. Krantz,David;Kifferstein, Brad. Water Pollution and Society, 2010. http://www.umich.edu/~gs265/society/waterpollution.htm (2010-03-04) 96 UNIT 4 VEGETABLES AND FRUITS Introduction "Eat your fruits and vegetables" is one of the tried and true recommendations for a healthy diet and for good reason. Eating plenty of vegetables and fruits can help you ward off heart disease and stroke, control blood pressure, prevent some types of cancer, avoid a painful intestinal ailment called diverticulitis, and guard against cataract and macular degeneration, two common causes of vision loss. What does "plenty" mean? More than most Americans consume. If you don't count potatoes—which should be considered a starch rather than a vegetable—the average American gets a total of just three servings of fruits and vegetables a day. The latest dietary guidelines call for five to thirteen servings of fruits and vegetables a day (2½ to 6½ cups per day), depending on one's caloric intake. (1) For a person who needs 2,000 calories a day to maintain weight and health, this translates into nine servings, or 4½ cups per day (2 cups of fruit and 2½ cups of vegetables). Over the past 30 years or so, researchers have developed a solid base of science to back up what generations of mothers preached (but didn't always practice themselves). Early on, fruits and vegetables were acclaimed as cancer-fighting foods. In fact, the ubiquitous 5 A Day message (now quietly changing to Fruits and Veggies: More Matters) seen in produce aisles, magazine ads, and schools was supported in part by the National Cancer Institute. The latest research, though, suggests that the biggest payoff from eating fruits and vegetables is for the heart. Figure 40. Fresh Fruits & Vegetables http://www.img.allposters.com/6/LRG/20/2012/DUP6D00Z.jpg (2010-03-23) 102 Vegetables, Fruits, and Cardiovascular Disease There is compelling evidence that a diet rich in fruits and vegetables can lower the risk of heart disease and stroke. The largest and longest study to date, done as part of the Harvard-based Nurses' Health Study and Health Professionals Follow-up Study, included almost 110,000 men and women whose health and dietary habits were followed for 14 years. The higher the average daily intake of fruits and vegetables, the lower the chances of developing cardiovascular disease. Compared with those in the lowest category of fruit and vegetable intake (less than 1.5 servings a day), those who averaged 8 or more servings a day were 30 percent less likely to have had a heart attack or stroke. (2) Although all fruits and vegetables likely contribute to this benefit, green leafy vegetables such as lettuce, spinach, Swiss chard, and mustard greens; cruciferous vegetables such as broccoli, cauliflower, cabbage, Brussels sprouts, bok choy, and kale; and citrus fruits such as oranges, lemons, limes, and grapefruit (and their juices) make important contributions. (2) When researchers combined findings from the Harvard studies with several other long-term studies in the U.S. and Europe, and looked at coronary heart disease and stroke separately, they found a similar protective effect: Individuals who ate more than 5 servings of fruits and vegetables per had roughly a 20 percent lower risk of coronary heart disease (3) and stroke, (4) compared with individuals who ate less than 3 servings per day. Vegetables, Fruits, and Blood Pressure High blood pressure is a primary risk factor for heart disease and stroke. As such, it's a condition that is important to control. Diet can be a very effective tool for lowering blood pressure. One of the most convincing associations between diet and blood pressure was found in the Dietary Approaches to Stop Hypertension (DASH) study. (5) This trial examined the effect on blood pressure of a diet that was rich in fruits, vegetables, and low-fat dairy products and that restricted the amount of saturated and total fat. The researchers found that people with high blood pressure who followed this diet reduced their systolic blood pressure (the upper number of a blood pressure reading) by about 11 mm Hg and their diastolic blood pressure (the lower number) by almost 6 mm Hg—as much as medications can achieve. More recently, a randomized trial known as the Optimal Macronutrient Intake Trial for Heart Health (Omni Heart) showed that this fruit and vegetable-rich diet lowered blood pressure even more when some of the carbohydrate was replaced with healthy unsaturated fat or protein. (6) Vegetables, Fruits, and Cancer Numerous early studies revealed what appeared to be a strong link between eating fruits and vegetables and protection against cancer. But because many of these were case-control studies, where people who already have a certain health outcome (cases) are compared to people who do not have that outcome (controls), it is possible that the results may have been skewed by problems inherent in these types of studies; people with illnesses, for example, often recall past behaviour differently from those without illness, which can lead to potential inaccuracy in the information that they provide to study investigators. Cohort studies, which follow large groups of initially healthy individuals for years, generally provide more reliable information than case-control studies because they don't rely on information from the past. And data from cohort studies have not consistently shown that a diet rich in fruits and vegetables prevents cancer in general. For example, in the Nurses' 103 Health Study and the Health Professionals Follow-up Study, over a 14-year period, men and women with the highest intake of fruits and vegetables (8+ servings a day) were just as likely to have developed cancer as those who ate the fewest daily servings (under 1.5). (2) A more likely possibility is that some types of fruits and vegetables may protect against certain cancers. A massive report by the World Cancer Research Fund and the American Institute for Cancer Research suggests that non-starchy vegetables—such as lettuce and other leafy greens, broccoli, bok choy, cabbage, as well as garlic, onions, and the like—and fruits "probably" protect against several types of cancers, including those of the mouth, throat, voice box, esophagus, and stomach; fruit probably also protects against lung cancer. (7) Specific components of fruits and vegetables may also be protective against cancer. For example, a line of research stemming from a finding from the Health Professionals Follow-up Study suggests that tomatoes may help protect men against prostate cancer, especially aggressive forms of it. (8) One of the pigments that give tomatoes their red hue—lycopene— could be involved in this protective effect. Although several studies other than the Health Professionals study have also demonstrated a link between tomatoes or lycopene and prostate cancer, others have not or have found only a weak connection. (9) Taken as a whole, however, these studies suggest that increased consumption of tomato-based products (especially cooked tomato products) and other lycopene-containing foods may reduce the occurrence of prostate cancer. (7) Lycopene is one of several carotenoids (compounds that the body can turn into vitamin A) found in brightly colored fruits and vegetables, and research suggests that foods containing carotenoids may protect against lung, mouth, and throat cancer. (7) But more research is needed before we know the exact relationship between fruits and vegetables, carotenoids, and cancer. Harvard School of Public Health. The Nutrition Source – Vegetables and Fruits, 2010. http://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/vegetables-fullstory/index.html (2010-03-10) 104 UNIT 5 SMART PACKAGING Intelligent Packaging for Fresh Fruit and Vegetables Fresh-cut produce continues to be one of the fastest growing segments of food retailing and while conventional film packaging is suitable for lettuce and prepared salads, it cannot cope with the high respiration rates of pre-cut vegetables and fruit, leading to early product deterioration. In the USA, novel breatheable polymer films are already in commercial use for fresh-cut vegetables and fruit. Landec Corporation supplies Intellipac packaging films that are acrylic side-chain crystallisable polymers tailored to change phase reversibly at various temperatures from 0-68 °C. As the side-chain components melt, gas permeation increases dramatically, and by further tailoring the package and materials of construction, it is possible to fine tune the carbon dioxide to oxygen permeation ratios for particular products. The final package is ‘smart’ because it automatically regulates oxygen ingress and carbon dioxide egress by transpiration according to the prevailing temperature. In this way, an optimum atmosphere is maintained around the product during storage and distribution, extending freshness and allowing shipping of higher quality products to the consumer. Self-Heating and Self-Chilling Packaging Improved convenience is a value-added function that customers are likely to pay extra for lifestyle change. Self-heating packages, for soup and coffee, for example, and self-cooling containers for beer and soft drinks have been under active development for more than a decade, but have yet to achieve commercial status. However, Crown Cork & Seal is pioneering the development of a self-chilling beverage can in conjunction with Tempra Technologies and development is nearing completion. The Crown/Tempra technology uses the latent heat of evaporating water to produce the cooling effect. The water is bound in a gel layer coating a separate container within the beverage can, and is in close thermal contact with the beverage. The consumer twists the base of the can to open a valve, exposing the water to the desiccant held in a separate, evacuated external chamber This initiates evaporation of the water at room temperature. The unit has been designed to meet a target specification set by major beverage customers cooling 300 ml of beverage in a 355 ml can by 16.7 °C in three minutes. This performance level has been achieved in laboratory tests and working samples are currently undergoing focus group trials with customers. Thermochromic Labelling Give a self-heating or self-cooling container a sensor to tell the consumer it is at the correct temperature and the package becomes ‘smart’ (such packaging is currently under development). The most common use of a thermochromic ink dot indicates that the product is at the correct serving temperature following refrigeration or microwave heating. Plastic containers of pouring syrup for pancakes can be purchased in the USA that are labelled with a thermochromic ink dot to indicate that the syrup is at the right temperature following microwave heating. Similar examples can be found on supermarket shelves with beer bottle labels that incorporate thermochromic-based designs to inform the consumer when a refrigerated beer is cold enough to drink. Packing,S. Smart Packaging-Intelligent Packaging for Food, 2003. http://www.azom.com/Details.asp?ArticleID=2152 (2010-03-10) 105 UNIT 7 FOOD HYGIENE As part of the revision of legislation on the hygiene of foodstuffs ("hygiene package"), this Regulation focuses on defining the food safety objectives to be achieved, leaving the food operators responsible for adopting the safety measures to be implemented in order to guarantee food safety. ACT Regulation (EC) No 852/2004 of the European Parliament and of the Council of 29 April 2004 on the hygiene of foodstuffs. SUMMARY This revision of Community legislation concerns food hygiene rules as contained in Council Directive 93/43/EEC, with a view to establishing a comprehensive and integrated policy covering all food from the farm to the point of sale to the consumer. Scope This Regulation seeks to ensure the hygiene of foodstuffs at all stages of the production process, from primary production up to and including sale to the final consumer. It does not cover issues relating to nutrition or to the composition or quality of foodstuffs.This Regulation applies to food businesses but not to the primary production of food for private domestic use or the domestic preparation of foodstuffs for private consumption. Definitions 'Food hygiene': the measures and conditions necessary to control hazards and ensure fitness for human consumption of a foodstuff. 'Food safety': the assurance that food will not cause adverse health effects to the final consumer when it is prepared and eaten. 'Primary production': the production, rearing or growing of primary products up to and including harvesting, hunting, fishing, milking and all stages of animal production prior to slaughter. General and specific provisions All food business operators shall ensure that all stages for which they are responsible, from primary production up to and including the offering for sale or supply of foodstuffs to the final consumer, are carried out in a hygienic way in accordance with this Regulation. Food business operators carrying out primary production and certain associated activities shall comply with the general hygiene provisions of part A of Annex I. Derogations may be granted for small businesses, provided that they do not compromise achievement of the Regulation's objectives. These associated activities are: • the transport, handling and storage of primary products at the place of production, where their nature has not been substantially altered; • the transport of live animals, where this is necessary; 107 • transport, from the place of production to an establishment, of products of plant origin, fishery products and wild game, where their nature has not been substantially altered. In addition, food business operators carrying out activities other than primary production shall comply with the general hygiene provisions of Annex II. This Annex sets out the hygiene requirements for: • food premises, including outside areas and sites; • transport conditions; • equipment; • food waste; • water supply; • personal hygiene of persons in contact with food; • food; • wrapping and packaging; • heat treatment, which may be used to process certain foodstuffs; • training of food workers. Member States may adapt the requirements laid down in Annex II to accommodate the needs of food businesses situated in regions suffering from special geographical constraints or affected by supply difficulties which are serving the local market, or to take account of traditional methods of production and the size of farms. The objectives of food hygiene shall not however be compromised. In addition, all food business operators shall comply with the provisions of Regulation (EC) No 853/2004 on specific hygiene rules for food of animal origin and, where appropriate, certain specific rules concerning microbiological criteria for foodstuffs, temperature control and compliance with the cold chain, sampling and analysis. The HACCP system Food business operators (other than at the level of primary production) shall apply the principles of the system of hazard analysis and critical control points (HACCP) introduced by the Codex Alimentarius (code of international food standards drawn up by the United Nations Food and Agriculture Organisation). These principles prescribe a certain number of requirements to be met throughout the cycle of production, processing and distribution in order to permit, via hazard analysis, identification of the critical points which need to be kept under control in order to guarantee food safety: • identify any hazards that must be prevented, eliminated or reduced to acceptable levels; • identify the critical control points at the step or steps at which control is essential; • establish critical limits beyond which intervention is necessary; • establish and implement effective monitoring procedures at critical control points; • establish corrective actions when monitoring indicates that a critical control point is not under control; • implement own-check procedures to verify whether the measures adopted are working effectively; • keep records to demonstrate the effective application of these measures and to facilitate official controls by the competent authority. Guides to good practice and guides to the application of HACCP 108 Member States shall encourage the development of national guides to good practice by food business operators, which shall include guidance on compliance with the general rules of hygiene and the HACCP principles. Member States shall assess such national guides to ensure that their contents are practicable, that they have been developed having regard to the general principles of food hygiene of the Codex Alimentarius and that all interested parties have been consulted. Those national guides deemed to comply with these requirements shall be forwarded to the Commission. Where a Member State or the Commission considers that there is a need for uniform Community guides, the Commission shall consider the case for such guides. The Standing Committees set up to assist the Commission shall ensure that the contents of these guides are practicable, that they have been developed having regard to the general principles of food hygiene of the Codex Alimentarius and of national guides, and that all interested parties have been consulted. Regulation (EC) No 852/2004 of the European Parliament and of the Council of 29 April 2004 on the hygiene of foodstuffs, 2010. http://europa.eu/legislation_summaries/food_safety/veterinary_checks_and_food_hygiene/f84 001_en.htm (2010-03-01) 109 UNIT 8 CARBOHYDRATE METABOLISM Many aspects of biochemistry and physiology have to do with the breakdown and synthesis of simple sugars, oligosaccharides, and polysaccharides, and with the transport of sugars across cell membranes and tissues. The breakdown or dissimilation of simple sugars, particularly glucose, is one of the principal sources of energy for living organisms. The dissimilation may be anaerobic, as in fermentations, or aerobic, that is, respiratory. In both types of metabolism, the breakdown is accompanied by the formation of energy-rich bonds, chiefly the pyrophosphate bond of the coenzyme adenosine triphosphate (ATP), which serves as a coupling agent between different metabolic processes. In higher animals, glucose is the carbohydrate constituent of blood, which carries it to the tissues of the body. In higher plants, the disaccharide sucrose is often stored and transported by the tissues. Certain polysaccharides, especially starch and glycogen, are stored as endogenous food reserves in the cells of plants, animals, and microorganisms. Others, such as cellulose, chitin, and bacterial polysaccharides, serve as structural components of cell walls. As constituents of plant and animal tissues, various carbohydrates become available to those organisms which depend on other living or dead organisms for their source of nutrients. Hence, all naturally occurring carbohydrates can be dissimilated by some animals or microorganisms. Certain carbohydrates cannot be used as nutrients by humans. For example, cellulose cannot be digested by humans or other mammals and is a useful food only for those, such as the ruminants, that harbour cellulose-decomposing microorganisms in their digestive tracts. The principal dietary carbohydrates available to humans are the simple sugars glucose and fructose, the disaccharides sucrose and lactose, and the polysaccharides glycogen and starch. Lactose is the carbohydrate constituent of milk and hence one of the main sources of food during infancy. The disaccharides and polysaccharides that cannot be absorbed directly from the intestine are first digested and hydrolyzed by enzymes, glycosidases, secreted into the alimentary canal. The simple sugars reach the intestine or are produced there through the digestion of oligosaccharides. They are absorbed by the intestinal mucosa and transported across the tissue into the bloodstream. This process involves the accumulation of sugar against a concentration gradient and requires active metabolism of the mucosal tissue as a source of energy. The sugars are absorbed from the blood by the liver and are stored there as glycogen. The liver glycogen serves as a constant source of glucose in the bloodstream. The mechanisms of transport of sugars across cell membranes and tissues are not yet understood, but they appear to be highly specific for different sugars and to depend on enzymelike components of the cells. The degradation of monosaccharides may follow one of several types of metabolic pathways. In the phosphorylative pathways, the sugar is first converted to a phosphate ester (phosphorylated) in a reaction with ATP. The phosphorylated sugar is then split into smaller units, either before or after oxidation. In the non-phosphorylative pathways, the sugar is usually oxidized to the corresponding aldonic acid. This may subsequently be broken down either with or without phosphorylation of the intermediate products. Among the principal intermediates in carbohydrate metabolism are glyceraldehyde-3-phosphate and pyruvic acid. The end products of metabolism depend on the organism and, to some extent, on the environmental conditions. Besides cell material the products may include carbon dioxide (CO2), alcohols, organic acids, and hydrogen gas. In the so-called complete oxidations, CO2 is 110 the only excreted end product. In incomplete oxidations, characteristic of the vinegar bacteria and of certain fungi, oxidized end products such as gluconic, ketogluconic, citric, or fumaric acids may accumulate. Organic end products are invariably found in fermentations. The amount of biosynthesis and mechanical work that an organism can do at the expense of a given amount of sugar is many times greater in respiration than in fermentation. The principal phosphorylative pathway involved in fermentations is known as the glycolytic, hexose diphosphate, or Embden-Meyerhof pathway (see illustration). This sequence of reactions is the basis of the lactic acid fermentation of mammalian muscle and of the alcoholic fermentation of yeast. For every molecule of glucose fermented through the glycolytic sequence, two molecules of ATP are used for phosphorylation, while four are produced. Thus, fermentation results in the net gain of two energy-rich phosphate bonds as ATP at the expense of inorganic phosphate esterified. The excess ATP is converted back to ADP and inorganic phosphate through coupled reactions useful to the organism, such as the mechanical work done by the contraction of muscle or biosynthetic reactions associated with growth.lycolysis in lactic acid fermentation The oxidative or respiratory metabolism of sugars differs in several respects from fermentative dissimilation. First, the oxidative steps, that is, the reoxidation of NADH, are linked to the reduction of molecular oxygen. Second, the pyruvic acid produced through glycolytic or other mechanisms is further oxidized, usually to CO2 and H2O. Third, in most aerobic organisms, alternative pathways either supplement or completely replace the glycolytic sequence of reactions for the oxidation of sugars. Where pyruvic acid appears as a metabolic intermediate, it is generally oxidatively decarboxylated to yield CO2 and the twocarbon acetyl fragment which combines with coenzyme A. The acetyl group is then further oxidized via the Krebs cycle. The principal alternative pathways by which sugars are dissimilated involve the oxidation of glucose-6-phosphate to the lactone of 6phosphogluconic acid and are known as the hexose monophosphate pathways. The metabolism of simple sugars other than glucose usually involves the conversion of the sugar to one of the intermediates of the phosphorylative pathways described for glucose metabolism. For example, fructose may be phosphorylated to fructose-6-phosphate, which can then be degraded via the glycolytic pathway or converted to glucose-6-phosphate and oxidized through the hexose monophosphate pathway. The dissimilation and biosynthesis of the oligosaccharides are effected through the enzymatic cleavage or formation of glycosidic bonds between simple monosaccharide constituents of the complex carbohydrates. The principal types of enzyme which split or synthesize glycosidic bonds are the hydrolases or glycosidases, phosphorylases, and transglycosylases. The enzymes are generally highly specific with respect to the glycosidic portion, or moiety, and the type of linkage of the substrates which they attack. The essential function of all three types of enzymes is the transfer of the glycosyl moiety of the substrate to an appropriate glycosyl acceptor. The phosphorylases catalyze the reversible phosphorolysis of certain disaccharides, polysaccharides, and nucleosides by transferring the glycosyl moieties to inorganic phosphate. The breakdown of glycogen and starch by the enzymes known as amylophophorylases is an example of biologically important phosphorolytic reactions. The Free Dictionary. Carbohydrate Metabolism, 2010. http://encyclopedia2.thefreedictionary.com/Carbohydrate+metabolism (2010-03-23) 111