Carbohydrates B.3

1. CarbohydratesB.3

2. Introduction • most abundant class of biological molecules • range from simple sugars (glucose) to complex carbohydrates (starch) • major functions: (B.3.4) • energy source: glucose converted into ATP • energy storage/reserves: glycogen • precursor for molecules such as DNA

3. Monosaccharides(B.3.1 and 2) • simplest sugars (single sugars) • empirical formula is (CH2O) • contain a ketone, C=O (fructose) or aldehyde, H-C=O (glucose) • contain at least two hydroxyl groups (-OH) • can be straight chains or cyclic form • two common monosaccharides • both C6H12O6 • glucose • fructose

4. Glucose on different sides of ring both on same side of ring

6. Fructose

8. Condensation of monosaccharides to form disaccharides and polysaccharides (B.3.3 and B.3.5) • example of a typical condensation reaction • A-OH + B-OH ===> H2O + A-O-B • (2 monosaccharides => water + 1 disaccharide)

9. requires enzymes • the hydroxyl (-OH) of two monomers are brought together and the H of one and the OH of the other come together to make H2O • the remaining O from one of the monomers bonds the two together in a bond called a glycosidic linkage

10. Hydrolysis • the reverse of condensation • the decomposition of a substance by the insertion of water molecules between certain of its bonds. • food is digested by hydrolysis

11. Disaccharides • double sugar (contains 2 monosaccharides) • three common disaccharides: 1. sucrose - common table sugar glucose + fructose 2. lactose - major sugar in milk glucose + galactose 3. maltose - product of starch digestion glucose + glucose

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17. Polysaccharides (3 types) • longer chains of simple sugars made of glucose • serve principally as food storage and structural molecules in plants • 3 Types of Polysaccharides 1. Starches (plants) • polymers of glucose molecules • serve as storage depots of glucose • two forms • amylose- water soluble, straight chains, thousands of glucoses • amylopectin- insoluble, branched chains, up to millions of glucoses

18. glucose polymer with a(14) linkages, and branches formed by a (16) linkages glucose polymer with onlya(14) linkages.

19. 2. Glycogen (animals) • a short-term storage polysaccharide for animals • highly branched glucose units put together that are broken down to meet energy demands of the body

20. 3. Cellulose (plants) • most abundant polysaccharide on Earth • the major structural material of which plants are made (wood and plant fibers) • insoluble and has great tensile strength because the hydroxyls (-OH) are reversed on successive glucoses compared to other polysaccharides

21. plant cell walls are among the strongest of biological structures • most organisms can’t break cellulose down into simple sugars because they don’t have the enzyme cellulase which is necessary to hydrolyze the glycosidic linkages

22. Dietary fiber B.3.6-7 • dietary fiber is plant material that we ingest but are not able to digest • passes through the gut relatively intact, as we do not possess cellulase enzymes capable of hydrolysing it • bacteria in our gut can digest it somewhat • example: cellulose

24. importance in our diet • helps “bulk” move through the large intestine more eaisly • prevent constipation and diverticulosis (bulges in the colon at weak places leading to pain) • may prevent irritable bowel syndrome (IBS) • may prevent hemorrhoids • may cause a “full feeling” and therefore decrease chance of obesity • may help prevent Crohn’s desease