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carbohydrates n.
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Carbohydrates

Carbohydrates

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Carbohydrates

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  1. Carbohydrates

  2. Carbohydrates • Composed of carbon, hydrogen, oxygen • General formula Cx(H2O)y • Two types: simple sugars and condensation polymers • Functions: • Energy • Precursors for metabolic rxns • Storage • Structural material (plants)

  3. Monosaccharides • Simple sugars • Soluble in water (glucose, fructose) • Classified by number of carbons • Contain two or more hydroxyl groups and one carbonyl group • Exist in chain or ring form • Hydroxyl group in ring form can be either α (projected downward) or β (projected upward)

  4. + D-fructose α-D-fructose β-D-fructose

  5. Disaccharides • Two simple sugars linked together • Soluble in water, hydrolysed by acid hydrolysis or enzymes • Condensation reaction! • Resulting bond: glycosidic link (1-4 link b/c C1 bonded to C4) • Lactose: beta-glucose + beta-galatose • Maltose: alpha-glucose + alpha-glucose • Sucrose: alpha-glucose + beta-fructose

  6. Polysaccharides • Long chains of monosaccharide units held together by glycosidic bonds • Insoluble in water, ideal for storage • 3 common polysaccharides • Starch (alpha-glucose), contains amylose and amylopectin, storage carbohydrate in plants (potato, rice, flour) • Glycogen (alpha-glucose), animal starch, found in liver, muscles • Cellulose (beta-glucose), structural material in plants

  7. amylose amylopectin glycogen cellulose

  8. Starch vs. Cellulose • Polymers of glucose • Starch: alpha-glycosidic links • Cellulose: beta-glycosidic links • Different linkage forms uncoiled linear structure w/ alternating glucose monomers: hydroxyl groups form H bonds with hydroxyl of other parallel cellulose • Cannot digest cellulose b/c enzyme cellulase not produced in humans and most mammals

  9. Dietary Fiber! • Plant material • Cellulose, pectin, waxes, lignin • Cannot hydrolyze b/c lack cellulase enzyme • Why is it important? • Prevention! • Irritable bowel syndrome • Constipation • Hemorrhoids • Colorectal cancer