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Chapter 16 Food: Those Incredible Edible Chemicals Food • Three main classes: – Carbohydrates – Fats – Proteins • Also need: – Water – Fiber – Vitamins – Minerals Chapter 16 2 Carbohydrates • Sugars – Used as sweetener – Absorbed directly into bloodstream • Come in several forms: glucose, fructose, sucrose • Lactose, milk sugar, digested by nearly all human babies, but few adults lack enzyme to start breakdown Chapter 16 3 Complex Carbohydrates • Starch: digestible polymer of glucose – Releases glucose when broken down – Supply 4 kcal/gram – Store small amounts in liver and muscle: glycogen • Cellulose: indigestible polymer of glucose – Also known as fiber – Most abundant carbohydrate – No caloric value Chapter 16 4 Fats • High-energy food – 9 kcal/gram • Build and maintain cell membranes • Mainly triglycerides – Ester of glycerol and fatty acids • Stored in adipose tissue – Insulate vital organs from shock – Insulate body against temperature changes Chapter 16 5 Chapter 16 6 Saturated Fats • Implicated in arteriosclerosis – Hardening of arteries • Strong correlation between them – Typically need cholesterol as well • Deposits form on inner walls of arteries • Blood clots get lodged – Stroke, if it occurs in brain – Heart attack, if in heart Chapter 16 7 Lipoprotein • Group of proteins combined with a lipid – typically triglycerides and cholesterol • Classified according to density Chapter 16 8 Fats and Cholesterol in Blood • Not all fats are bad – Prefer mono-unsaturated fats found in olive and canola oil – Polyunsaturated fats may also be good • Natural unsaturated fats are cis isomers • Adding hydrogen may produce trans isomers – May raise cholesterol levels Chapter 16 9 Chapter 16 10 Proteins • Broken down into amino acids – Used mainly to produce useful proteins – Produce: muscle, hair, enzymes, … – Only excesses used for energy production • Body can synthesize all but eight amino acids – Essential amino acids – Combined plant sources to get all of them Chapter 16 11 Minerals • Also known as dietary minerals – about 4% weight of human body • Some used for bulk and structural uses • Ultra-trace elements: need only at very low levels – Some have no known function • Too much of any mineral may be toxic Chapter 16 12 Chapter 16 13 Vitamins • Specific organic compounds required in the diet to prevent specific diseases • Two broad classes • Fat soluble – Store excess – May lead to overdose • Water soluble – Excrete excess – May be lost during cooking Chapter 16 14 Dietary Fiber • Takes up space in stomach • Insoluble fiber: made of cellulose – May prevent some digestive problems • Soluble fiber: made of sticky materials – Help remove bile acids that digest fat – May slow sugar absorption Chapter 16 15 Water • Makes up most of the food we eat • Require 1–1.5 L of water per day – May need more after exercise or on hot days • Carbonated beverages long ago replaced water as beverage consumed most in U.S. Chapter 16 16 Starvation • Human body deprived of food • Weakening during starvation, makes you more susceptible to disease • Body consumes itself in order to get energy – Glycogen – Fat tissue – Muscle Chapter 16 17 Processed Food • Processing removes some of the nutrients • Nutrients may also be removed by cooking process • Manufacturers may add important vitamins and minerals back to food – Not all nutrients are necessarily added back Chapter 16 18 Food Additives • Substances other than basic foodstuffs that are present in food as a result of some aspect of production, processing, packaging, or storage • Sugar, salt, and corn syrup used in greatest amounts • Used since ancient historic times • In U.S., regulated by FDA Chapter 16 19 Additives • Enrichment: adding nutrients back to foods • Many spices and flavoring agents added to improve taste – Some flavoring agents have been purified and used directly – When used in moderation, present little in health hazards Chapter 16 20 Artificial Sweeteners • Developed to help combat obesity • Tend to be polyhydroxy compounds • Varying amounts of sweetening ability Chapter 16 21 Flavor Enhancers • Do not have much flavor • Enhance other flavors • Most common one is table salt – Enhances sweetness and may mask bitterness and sourness • Also use monosodium glutamate (MSG) Chapter 16 22 Spoilage Inhibitors • Inhibit growth of bacteria and molds – Common ones include NaNO2 and SO2 • Prevent oxidation of foods – Occurs when fats go rancid – Usually occurs by production of free radicals – Use antioxidants to prevent this from happening Chapter 16 23 Food Coloring • Expectation that foods will have certain colors – Would you drink bright blue milk? • Many dyes exist to color food • Label must clearly indicate if artificial colors are present Chapter 16 24 Poisons in Food • Some are natural – Botulism toxin – Oxalic acid – Aflatoxins • Some cause cancer – Aflatoxins • Some are toxic – Botulism toxin Chapter 16 25 Incidental Additives • Get in accidentally during production, packaging, or storage • May include: pesticide residues, insect parts, and antibiotics given to animals – Antibiotics used to promote weight gain – Government-accepted levels of insect parts in grain – impossible to remove all Chapter 16 26 Life Without Additives? • Food would be blander – No spices or flavor enhancers • More rapid spoilage of food – Would reduce amount of food available • Possible vitamin or mineral deficiencies Chapter 16 27 Growing Food Chapter 16 28 Fertilizers • Three primary plant nutrients: – Nitrogen, potassium, and phosphorus • Add them to increase crop production • Replace lost nutrients in soil • Allows support of more people on a given area of farmland Chapter 16 29 Nitrogen • Some plants fix nitrogen out of air – Legumes: e.g., clover and peas • Rotate with nitrogen-consuming crops – corn • Use chemical fertilizers to avoid having to alternate crops in a given field – Typically use ammonia-based fertilizers Chapter 16 30 Phosphorus • Often limiting growth factor in plants • Used as fertilizer since ancient times • Historically, produced from bones, guano, or fish meal • Produced today from phosphatecontaining rock – ~90% used for agriculture Chapter 16 31 Potassium Fertilizer • Usually abundant • Produced from various mines around world • Essential to fluid balance of the cell Chapter 16 32 Other Essential Elements Chapter 16 33 War Against Pests • Insecticides: substances that kill insects • Pesticides: substances that kill organisms that we consider pests • Early pesticides contained arsenic • May have some toxicity to other creatures Chapter 16 34 DDT: Dream Insecticide • • • • Easy to produce Highly effective Did not show toxicity to humans Used extensively during World War II – Slowed down spread of malaria, kept lice population in check – Saves millions of lives Chapter 16 35 Decline and Fall of DDT • Overuse led to insects developing resistance to DDT • Pesticide persistence: substance did not readily break down in environment • Toxic to fish as well as insects • Also get biological magnification Chapter 16 36 Biological Magnification Chapter 16 37 Biological Insect Controls • Use natural enemies to get rid of pests • May not be as effective as chemical pesticides • Possible to insert genes that confer pest resistance • Many ways to do this – Sterilization – Pheromones – Juvenile hormones Chapter 16 38 Herbicides and Defoliants • Herbicides: kill weeds – Allow for more abundant harvests • Defoliants: cause leaves to fall off plants – Used to help harvest of crops – Example: makes harvesting of cotton easier • May see buildup of resistance Chapter 16 39 Energy Flow of Modern Agriculture Chapter 16 40 Sustainable Agriculture • Organic farming uses less energy but requires more labor and produces fewer crops • Sudden switch to organic farming could be disastrous Chapter 16 41 Malthusian Mathematics • Basically said: Population grows faster than food supply; humans must control birthrate • Arises from difference in arithmetic growth vs. geometric growth Chapter 16 42 Can We Feed the World? • Increased food production since Malthus’ time • Still hungry in this day and age • Caused by: war, poverty, and lack of arable land • Modern agriculture dependent on cheap energy Chapter 16 43