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Carbohydrates

Carbohydrates. Carbohydrates serve as fuel and building material Carbohydrates Include both sugars and their polymers. Sugars. Monosaccharides Are the simplest sugars Can be used for fuel Can be converted into other organic molecules Can be combined into polymers.

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Carbohydrates

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  1. Carbohydrates • Carbohydrates serve as fuel and building material • Carbohydrates • Include both sugars and their polymers

  2. Sugars • Monosaccharides • Are the simplest sugars • Can be used for fuel • Can be converted into other organic molecules • Can be combined into polymers

  3. Triose sugars(C3H6O3) Pentose sugars(C5H10O5) Hexose sugars(C6H12O6) H H H H O O O O C C C C H C OH H C OH H C OH H C OH H C OH H C OH HO C H HO C H Aldoses H H C OH H C OH HO C H H C OH H C OH H C OH Glyceraldehyde H C OH H C OH H Ribose H H Glucose Galactose H H H H C OH H C OH H C OH C O C O C O HO C H H C OH H C OH H C OH Ketoses H C OH H Dihydroxyacetone H C OH H C OH H C OH H Ribulose H Figure 5.3 Fructose Examples of monosaccharides

  4. O H 1 C 6CH2OH 6CH2OH 2 CH2OH H C OH 5C H 5C O O 6 3 H O H H H H H 5 HO C H H HOH HOH 4 4C 1 C 1C 4C 4 1 OH H H H C OH O HO OH 3 2 OH OH 5 OH 2 C C 3 C 2C 3 OH H C H OH 6 H H OH OH H C OH H Figure 5.4 (a) Linear and ring forms. Chemical equilibrium between the linear and ring structures greatly favors the formation of rings. To form the glucose ring, carbon 1 bonds to the oxygen attached to carbon 5. Monosaccharides • May be linear • Can form rings

  5. Disaccharides • Consist of two monosaccharides • Are joined by a glycosidic linkage

  6. (a) Dehydration reaction in the synthesis of maltose. The bonding of two glucose units forms maltose. The glycosidic link joins the number 1 carbon of one glucose to the number 4 carbon of the second glucose. Joining the glucose monomers in a different way would result in a different disaccharide. CH2OH CH2OH CH2OH CH2OH O O O O H H H H H H H H 1–4glycosidiclinkage HOH HOH HOH HOH 4 1 H H H H OH OH O H OH HO HO OH O H H H H OH OH OH OH H2O Glucose Maltose Glucose CH2OH CH2OH CH2OH CH2OH O O O O 1–2glycosidiclinkage H H H H H H HOH HOH 2 1 H H HO H HO H Dehydration reaction in the synthesis of sucrose. Sucrose is a disaccharide formed from glucose and fructose.Notice that fructose,though a hexose like glucose, forms a five-sided ring. (b) OH H O O HO CH2OH HO CH2OH H OH H H OH H OH OH H2O Glucose Sucrose Fructose Figure 5.5 • Examples of disaccharides

  7. Polysaccharides • Polysaccharides • Are polymers of sugars • Serve many roles in organisms

  8. Storage Polysaccharides • Starch • Is a polymer consisting entirely of glucose monomers

  9. Chloroplast Starch 1 m Amylose Amylopectin (a) Starch: a plant polysaccharide Figure 5.6 • Is the major storage form of glucose in plants

  10. Giycogen granules Mitochondria 0.5 m Glycogen Figure 5.6 (b) Glycogen: an animal polysaccharide • Glycogen • Consists of glucose monomers • Is the major storage form of glucose in animals

  11. Structural Polysaccharides • Cellulose • Is a polymer of glucose

  12. H O CH2OH C CH2OH OH H C H O O OH H H H H HO C H 4 4 1 OH H OH H HO OH H HO H C OH H OH OH H C OH H  glucose C  glucose H OH (a)  and  glucose ring structures CH2OH CH2OH CH2OH CH2OH O O O O 1 4 4 4 1 1 1 OH OH OH OH O O O O HO OH OH OH OH (b) Starch: 1– 4 linkage of  glucose monomers CH2OH CH2OH OH OH O O O O OH OH OH OH 4 O 1 HO OH O O CH2OH CH2OH OH OH (c) Cellulose: 1– 4 linkage of  glucose monomers Figure 5.7 A–C • Has different glycosidic linkages than starch

  13. About 80 cellulose molecules associate to form a microfibril, the main architectural unit of the plant cell wall. Cellulose microfibrils in a plant cell wall Microfibril Cell walls  0.5 m Plant cells OH OH CH2OH CH2OH O O O O OH OH OH OH O O O O O OH CH2OH OH CH2OH Cellulose molecules CH2OH OH CH2OH OH O O O O OH OH OH OH Parallel cellulose molecules are held together by hydrogen bonds between hydroxyl groups attached to carbon atoms 3 and 6. O O O O O OH CH2OH OH CH2OH CH2OH CH2OH OH OH O O O O OH OH OH OH O O O A cellulose molecule is an unbranched  glucose polymer. O O OH CH2OH OH CH2OH Figure 5.8 • Glucose monomer • Is a major component of the tough walls that enclose plant cells

  14. Figure 5.9 • Cellulose is difficult to digest • Cows have microbes in their stomachs to facilitate this process

  15. CH2OH O OH H H OH H H H NH O C CH3 OH (b) Chitin forms the exoskeleton of arthropods. This cicada is molting, shedding its old exoskeleton and emerging in adult form. (c) Chitin is used to make a strong and flexible surgical thread that decomposes after the wound or incision heals. (a) The structure of the chitin monomer. Figure 5.10 A–C • Chitin, another important structural polysaccharide • Is found in the exoskeleton of arthropods • Can be used as surgical thread

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