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BIOMOLECULES Substances found in living organism 5% 30% 65% Water Biomolecules Mineral salts Listening activity Listen and try to write down as many words as possible, above all the names of the four biomolecules. Then, answer the questions. https://youtu.be/hl9PtmbsAZg Transcript Biomolecules are the main components of our body and of the body of all living organisms. They are complex molecules, very complex in some cases, but they are part of our everyday life although most of us are not aware of this. In fact, together with vitamins and minerals, they are the basis of our nutrition. Carbohydrates, for example, contain sugar and polysaccharides. Sugars are compounds that can be found in fruit, but also in milk and many other kinds of food. Generally they are easily recognized by their sweet taste. Polysaccharides are not sweet, though they are made of sugars. However, they are the basis of nutrition for most human beings. They are the basic components of all such foods such as wheat, potatoes, corn, rice, but also pasta, bread and polenta. They can be found in many other kinds of foods for example legumes like beans, chickpeas, lentils and the like. Lipids are fatty acid substances such as the seasonings like oil and butter, but they can be found in high quantities in some kinds of meat, in eggs and in several vegetables such as avocado. They work mostly as reserve substances as they are very rich in energy. Proteins are perhaps the most varied and complex class of biomolecules. This is why several foods contain an amount of them, but in our diet the food which is rich in proteins are meat, eggs, fish and their by-products such as ham and salami. Among vegetables, legumes are an important source of proteins. The last class of biomolecules is that of nucleic acids. These include RNA and the well-known DNA. All cell contain an amount of DNA because, as you probably know, it works as hereditary memory. Each cells has its own quantity of DNA though this is not stored in a specific part of a living organism so, it is not particulalry important as an elementary source. In spite of that, all living beings contain it. Questions 1. What are biomolecules? 2. Why biomolecules are important together with vitamins and minerals? 3. Which are the four biomolecules mentioned in the track? 4. Which is the only biomolecule that is not important as a nutritional source? 5. In which food can we found sugar and how can we recognize it? 6. Polysaccharides are the basic component of which foods? 7. Which is the main function of lipids? 8. Which is the most varied and complex class of biomolecules? 9. Which biomolecules can we found in legumes? 10. What is the function of DNA? C A R B O H Y D R A T E S P R O T E I N S L I P I D S N U C L E I C A C I D S With the exception of the lipids, these biological molecules are polymers (poly, “many”; mer, “unit”) constructed by the covalent bonding of smaller molecules called monomers. MONOMERS condensation idrolysis POLYMER Polymers are formed from monomers by a series of condensation reactions that result in the formation of covalent bonds between monomers. A molecule of water is released with each covalent bond formed and energy is added to the system. MONOMERS condensation idrolysis POLYMERS The reverse of a condensation reaction is a hydrolysis reaction (hydro, “water”; lysis, “break”). Hydrolysis reactions result in the breakdown of polymers into their component monomers. Water reacts with the covalent bonds that link the polymer together. Hydrolysis releases energy. MONOMERS condensation idrolysis POLYMERS How the macromolecules function and interact with other molecules depends on the properties of certain chemical groups in their monomers, the functional groups. Each functional group has specific chemical properties, and when it is attached to a larger molecule, it confers those properties on the larger molecule. Because macromolecules are so large, they contain many different functional groups such as: https://www.youtube.com/watch?v=H8WJ2KENlK0 C A R B O H Y D R A T E S P R O T E I N S L I P I D S N U C L E I C A C I D S Carbohydrates usually have the general formula Cn(H2O)n which makes them appear as hydrates of carbon. BIOCHEMICAL ROLES • they are a source of energy ready to use or of stored energy that can be released in a form usable by organisms; • they serve as carbon skeletons that can be rearranged to form new molecules. CATEGORIES OF CARBOHYDRATE DEFINED BY THE NUMBER OF MONOMERS • Monosaccharides; • Disaccharides; • Oligosaccharides; • Polysaccharides. simple sugars complex sugars Monosaccharides (mono, “one”; saccharide, “sugar”) They are the monomers from which the larger carbohydrates are constructed. Pentoses five-carbon sugars • ribose • deoxyribose One oxygen atom is missing from carbon 2 in deoxyribose (de-, “absent”). The absence of this oxygen atom is an important distinction between RNA and DNA. Hexoses six-carbon sugars • glucose • fructose • galactose Disaccharides (di, “two”) They are constructed from two monosaccharides that are covalently bonded together by condensation reactions that form glycosidic linkages. Disaccharides (di, “two”) Sucrose Glc + Fru Maltose Glc + Glc Lactose Glc + Gal Oligosaccharides (oligo, “several”) They are made up of several (3–20) monosaccharides. They are often covalently bonded to proteins and lipids on the outer cell surface, where they serve as recognition signals. The different human blood groups (for example, the ABO blood types) get their specificities from oligosaccharide chains. Polysaccharides (poly, “many”) They are polymers made up of hundreds or thousands of monosaccharides. In contrast to proteins, polysaccharides are not necessarily linear chains of monomers. Polysaccharides (poly, “many”) They are all polysaccharides of glucose, but they have a different molecular structure. Cellulose Starch Glycogen Polysaccharides (poly, “many”) Polysaccharides in cells. Starch (vegetal) Cellulose (vegetal) Glycogen (animal) Starch is the principal energy storage compound of plants. Large starch aggregates called starch grains can be observed in the storage tissues of plant seeds. Glycogen is a water-insoluble, highly branched polymer of glucose. It is used to store glucose in the liver and muscles and is thus an energy storage compound for animals, as starch is for plants. Both glycogen and starch are readily hydrolyzed into glucose monomers, which in turn can be broken down to liberate their stored energy. Like starch and glycogen, cellulose is a polysaccharide of glucose. As the predominant component of plant cell walls, cellulose is an excellent structural material and it is by far the most abundant organic compound on Earth. Starch is easily degraded by the actions of enzymes. Cellulose, however, is chemically more stable and we can’t digest it. There is a fourth polysaccharide called chitin that is a polymer of glucose, too. It is a characteristic component of: • the cell walls of fungi • the exoskeletons of arthropods such as crustaceans (e.g., crabs, lobsters and shrimps) and insects. C A R B O H Y D R A T E S P R O T E I N S L I P I D S N U C L E I C A C I D S PROTEINS Proteins have very diverse roles, only two (energy storage and information storage) are not usually performed by them. PROTEINS All proteins are polymers made up of 20 aminoacids in different proportions and sequences. Proteins range in size from small ones such as insulin, which has 51 amino acids to huge molecules such as the muscle proteins, with thousands of aminoacids. Primary structure of insulin PROTEINS Proteins consist of one or more polypeptide chains— unbranched (linear) polymers of covalently linked amino acids. Each chain folds into a particular three-dimensional shape that depends on the sequence of amino acids present in the chain. AMINO ACIDS STRUCTURE Each amino acid has both a carboxyl functional group and an amino functional group attached to the same carbon atom. Also attached to the carbon atom are a hydrogen atom and a side chain, or R group. PROTEINS The R groups of amino acids contain functional groups that are important in determining the 3D structure and thus the function of the protein. The 20 amino acids found in living organisms are grouped and distinguished by their side chains. Nine of them are essential amino acids because they cannot be synthesized by the organism, and thus must be supplied in its diet. CONDENSATION REACTION When amino acids polymerize, the carboxyl and amino groups attached to the carbon atom are the reactive groups. The carboxyl group of one amino acid reacts with the amino group of another, undergoing a condensation reaction that forms a peptide linkage (also called a peptide bond). LEVELS of PROTEIN ORGANISATION LEVELS of PROTEIN ORGANISATION For example, Hemoglobin consist of four folded polypeptide chain that assemble themselves into a quaternary structure. FUNCTIONS • Enzymes catalyze (speed up) biochemical reactions • Structural proteins provide physical stability such as collagen FUNCTIONS • Signaling proteins hormones that control physiological processes such as insulin • Defensive proteins recognize and respond to nonself substances such as antibodies FUNCTIONS • Membrane transporters regulate passage of substances across cellular membranes • Transport proteins bind and carry substances within the organism such as hemoglobin that carry oxygen FUNCTIONS • Movement function actin and myosin for example, are involved in muscle contraction C A R B O H Y D R A T E S P R O T E I N S L I P I D S N U C L E I C A C I D S LIPIDS Lipids—colloquially called fats—are hydrocarbons that are insoluble in water because of their hydrophobic chains. They are not polymers in a strict chemical sense. CLASSIFICATION SIMPLE LIPIDS fats and oil COMPLEX LIPIDS Es. phospholipids OTHERS carotenoids, steroids, vitamins, waxes SIMPLE LIPIDS Chemically, fats and oils are called triglycerides. Triglycerides that are: • solid at room temperature (around 20°C) are called fats; • liquid at room temperature are called oils. SIMPLE LIPIDS Triglycerides are composed of two types of building blocks: fatty acids and glycerol. SIMPLE LIPIDS Glycerol is a small molecule with three hydroxyl (—OH) groups (thus it is an alcohol). A fatty acid is made up of a long hydrocarbon chain and a carboxyl group (— COOH), so it is a molecule with a hydrophilic end and a long hydrophobic tail. The technical term for this is amphipathic. A triglyceride contains three fatty acid molecules and one molecule of glycerol. SIMPLE LIPIDS Synthesis of a triglyceride involves three condensation (dehydration) reactions. In each reaction, the carboxyl group of a fatty acid bonds with a hydroxyl group of glycerol, resulting in a covalent bond called an ester linkage and the release of a water molecule. SIMPLE LIPIDS The three fatty acids in a triglyceride molecule need not all have the same hydrocarbon chain length or structure; some may be saturated fatty acids, whereas others may be unsaturated. In saturated fatty acids, all the bonds between the carbon atoms in the hydrocarbon chain are single. These fatty acid molecules are straight, and they pack together tightly. SIMPLE LIPIDS The triglycerides of animal fats tend to have many long-chain saturated fatty acids packed tightly together; these fats are usually solids at room temperature and have high melting points. SIMPLE LIPIDS In unsaturated fatty acids, the hydrocarbon chain contains one or more double bonds. Linoleic acid is an example of a polyunsaturated fatty acid that has two double bonds causing kinks in the molecule that prevent the unsaturated fat molecules from packing together tightly. The kinks are important in determining the fluidity and melting point of lipids. SIMPLE LIPIDS The triglycerides of plants, such as corn oil, tend to have short or unsaturated fatty acids. Because of their kinks, these fatty acids pack together poorly and have low melting points, and these triglycerides are usually liquids at room temperature. SIMPLE LIPIDS Fatty acids are excellent storehouses for chemical energy: when the C—H bond is broken, it releases energy that an organism can use for its own purposes, such as movement or building up other complex molecules. PHOSPHOLIPIDS Phospholipids contain fatty acids bound to glycerol by ester linkages. In phospholipids, however, a phosphate-containing compound replaces one of the fatty acids. The fatty acids are hydrophobic and tend to avoid water while the phosphate functional group is hydrophilic; for this the phospholipid is an amphipathic molecule. PHOSPHOLIPIDS PHOSPHOLIPIDS In an aqueous environment, phospholipids line up in such a way that the hydrophobic “tails” pack tightly together and the phosphatecontaining “heads” face outward. The phospholipids thus form a bilayer. Biological membranes have this kind of phospholipid bilayer structure. OTHERS The carotenoids are plants or animal pigments that traps light energy in leaves during photosynthesis. In humans, they are precursor of Vitamin A which is required for vision. Carotenoids are responsible for the colors of carrots, tomatoes, pumpkins, egg yolks, butter and autumn leaves. OTHERS The steroids are a family of organic compounds with multiple rings of carbons. The steroid cholesterol is an important constituent of membranes, helping maintain membrane integrity. Sex hormones are derived from cholesterol such as testosterone. OTHERS Vitamins are small molecules that are not synthesized by the human body and so must be acquired from the diet. For example, vitamin A is formed from the βcarotene found in orange and yellow vegetables. In humans, a deficiency of vitamin A leads to night blindness, which is a diagnostic symptom for the deficiency. Vitamins D, E, and K are also lipids. OTHERS Waxes are produced by birds and mammals as a waterproof coating that help them retain water and exclude pathogens. The shiny leaves of plants such as holly, familiar during winter holidays, also have waxy coatings. Bees make their honeycombs out of wax. BIOLOGICAL FUNCTIONS To sum up, they play a number of roles in living organisms: • Fats and oils store energy; • Phospholipids play important structural roles in cell membranes; • Carotenoids and chlorophylls help plants capture light energy BIOLOGICAL FUNCTIONS • Steroids play regulatory roles as hormones and vitamins; • Fat in animal bodies serves as thermal insulation; • Oil or wax on the surfaces of skin, fur, feathers, and leaves repels water and prevents excessive evaporation of water from terrestrial animals and plants. C A R B O H Y D R A T E S P R O T E I N S L I P I D S N U C L E I C A C I D S NUCLEIC ACIDS Nucleic acids are polymers specialized for the storage, transmission, and use of genetic information. CHEMICAL STRUCTURE Nucleic acids are polymers composed of monomers called nucleotides. A nucleotide consists of three components. P: phosphate group B: nitrogen-containing base Z: pentose sugar (ribose or deoxyribose) The pentose sugar deoxyribose differs from the ribose by the absence of one oxygen atom. CHEMICAL STRUCTURE There are 5 types of nitrogen-containing base: During the formation of a nucleic acid, a condensation reaction occurs between a pentose sugar and the phosphate on the next nucleotide. DNA molecules in humans contain hundreds of millions of nucleotides. https://webiebook.scuola.zanichelli.it/fro m-biochemistry-tobiotechnology/frombiochemistry-tobiotechnology-1/z43544v14-c00-01/z43544v14-p-00-01-05 There are two types of nucleic acids DNA deoxyribonucleic acid RNA ribonucleic acid DIFFERENCES between DNA and RNA SUGAR: in DNA, the pentose sugar is deoxyribose, which differs from the ribose found in RNA by the absence of one oxygen atom. BASES: four bases are found in DNA, A, C, G and T. RNA is also made up of four different monomers, but its nucleotides include U instead of T. STRAND STRUCTURE: RNA is generally single-stranded while DNA is double-stranded STRUCTURE of DNA DNA consists of two separate polynucleotide strands of the same length that are held together by hydrogen bonds between base pairs: thymine and adenine always pair (T-A) and cytosine and guanine always pair (C-G). the two polynucleotide strands form a “ladder” that twists into a double helix . The key differences among DNA molecules are their different nucleotide base sequences. DIFFERENCES in FUNCTION DNA is a purely informational molecule that encodes hereditary information and passes it from generation to generation. During cell division and reproduction, information flows from existing DNA to the newly formed DNA in a new cell or organism. In the non-reproductive activities of the cell, information flows from DNA to RNA to proteins. The information encoded in DNA is used to specify the amino acid sequences of proteins using RNA as an intermediary. This process is called gene expression. The central dogma of molecular biology is an explanation of the flow of genetic information within a biological system