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Carbohydrate Aulanni’am Laboratory of Biochemistry Brawijaya University Six Classes of Nutrients 1. 2. 3. 4. 5. 6. Carbohydrate Protein Fat Vitamins Minerals Water Carbohydrates and Relation to Health 1. Dietary fiber and prevention of chronic diseases 2. Carbohydrates and dental health 3. Carbohydrates and diabetes Carbohydrates and weight loss??? 1. Carbohydrates and Prevention of Chronic Diseases Health Benefits of Fiber Reduce the risk of • Heart disease • Diabetes • Diverticular disease (gastrointestinal / GI) Other • Relieves Constipation • Hemorrhoids • Lowers the GI/GL • Makes you feel full Complex Carbohydrates Starch digestible plant polysaccharide Fiber indigestible polysaccharide residues of food • Cannot be broken down by human digestive enzymes • some broken down by bacteria in the digestive tract • few, if any, calories because not digested • Examples: cellulose, hemicellulose, pectin, gums Polysaccharide: long chain of 10 or more glucose molecules linked together; the chains can be straight or branched; another term for complex carbohydrates Dietary Fiber • Components of the cell walls of plants • cereal grains, fruits, vegetables • Polymer of monosaccharides • Human digestive enzymes cannot break down • Cellulose = ~3000 glucose Dietary Fiber - Two groups 1. Insoluble • • fibers that mostly do not dissolve in water not digested by bacteria in the large intestine 2. Soluble • • fibers that either dissolve or swell in water or are metabolized by bacteria in the large intestines Fiber Sources Soluble Fiber - Heart Insoluble Fiber – GI tract ● Oatmeal ● Whole grains ● Nuts and seeds ● Wheat bran ● Legumes • dried peas • beans ● Vegetables ● Fruits • apples • pears • • carrots celery Degree of polymerization • Monosaccharides • Storage, energy modules, metabolic intermediates • Disaccharides, trisaccharides • Storage • Oligosaccharides • Molecular Recognition • Polysaccharides • Structure, storage Fisher Projections of chiral monosaccharides • Next-to-bottom carbon hydroxyl extends to the right --- a D sugar; cf. with L amino acid CHO H OH CH 2OH D-glyceraldehyde COOH H2N H CH3 L-valine fig 9-3a fig 9-3b Hemiacetal/-ketal structures of monosaccharides • Reaction of an aldehyde or ketone with an alcohol • favorable intramolecular reaction fig 9-5 Intramolecular hemiacetals/ketals of monosaccharides are RINGS OH O HO stereo CHO H HO H H HO OH OH OH H OH OH OH CH 2OH open chain O H H H H OH H HO OH H O HO HO H OH Haworth chair OH H H H OH OH Anomers • Sugars that vary in configuration about the anomeric (aldehydic or ketonic) carbon • Convention: = hydroxyl down, = hydroxyl up fig 9-6 Fig 9-7 Hexose derivatives • Amino sugars • Acetamido sugars • Deoxy sugars • Fucose, rhamnose, abequose • Other glycosidic additives • Lactic acid • Oxidized sugars • Sugar phosphates Fig 9-9 Reducing sugars • Aldehydes are oxidized by mild agents • Cu2+ + aldehyde (or -hydroxyketone) Cu+ + acid • Disaccharides react more slowly Fig 9-10 Disaccharides • Glycosidic linkage • Acetal (or ketal) formed. 2nd monosaccharide acts as an alcohol Fig 9-5 (repeat) • Reducing • one anomeric C not glycosidically linked • Nonreducing • Both anomeric C’s linked (fructose, trehalose) Disaccharide nomenclature • Nonreducing end on left • Linkage –(nm)• Reducing end Note that nonreducing end configuration is fixed Reducing end can mutarotate, thus 1st component given as - or -, 2nd ambiguous (next slide) Fig 9-11 Table 9-1 Important disaccharides • • • • Maltose Lactose Sucrose Trehalose Fig 9-12 Table 9-2 Storage polysaccharides • Plants • Starch • Amylose – llinear polyglucose, -1,4 linked (-Dglucopyranosyl-(14)-…), M ~ 106 • Amylopectin –polyglucose, -1,4 linked, -1,6 branched 1 per 24-30, M ~ 108 • Animals • Glycogen • polyglucose, -1,4 linked, -1,6 branched 1 per 24-30, M ~ 106 Fig 9-15 b Fig 9-14 1.0 m 0.10 m fig 9-15 Structural Polysaccharides • Plants • Cellulose – linear polyglucose • 1,4 linked • M ~ 106 • Certain exoskeletons • Chitin – linear poly(N-acetyl-D-glucosamine) • 1,4 linked Fig 9-17a and 9-18 Cellulose Chitin Structural polysaccharides, cont • Bacterial cell walls – peptidoglycans • Extracellular matrix of multicellular animals glycosaminoglycans Fig 9-19 Fig 9-20 Sugar-protein and sugar-lipid conjugates • Glycoconjugates • Proteoglycans • Glycosaminoglycans bound to proteins • Glycoproteins • Oligosaccharides bound to proteins • Glycolipids • Oligosaccharides bound to lipids (heads of membrane lipids) Fig 9-29 Fig 9-27 2. Carbohydrates and Dental Health Dental Caries (Cavities) Bacterial + Sugars Cavities MECHANISM • Bacterial acid dissolves enamel • Carbohydrate serves as food for bacteria • Plaque on teeth – sugars stay in but acids don’t go out CARIOGENIC FOOD FACTORS • Fermentable – contains sugars • Sticky • Stays in mouth a long time (think taffy) 3. Carbohydrates and Diabetes Diabetes: An inability to regulate blood glucose levels • A disease in which an individual does not produce or properly use insulin Results in: • abnormally high levels of glucose in blood Because of: • lack or ineffectiveness of insulin hormone that is needed to convert sugar, starches and other food into energy needed for daily life the true cause continues to be a mystery, although both genetics and environmental factors such as obesity and lack of exercise play roles Type I vs. Type II Diabetes Type 1 – Insulin Dependent Type 2 – Non- Insulin Depend Incidence Insulin 5-10% of cases Pancreas unable to make insulin to meet needs Risk factor Genetic predisposition + environmental factors 90-95% of cases Maybe insufficient insulin or cells maybe unresponsive to insulin Genetic predisposition + obesity Dietary intervention Weight loss intervention Treatment Insulin injections Dietary Intervention • Reduce the amount of simple sugars • Eat foods w/ dietary fiber Person will lose weight Person is always hungry Increase in obesity Carbohydrates role in blood glucose Glycemic Index • A numerical system • Measures extent of rise in circulating blood sugar a carbohydrate triggers • GI number, blood sugar response Glycemic Index estimate of how quickly food affects your blood sugar Glycemic Index High GI Low GI > 70 < 55 potatoes, white bread pasta, whole grain bread Not just about individual foods it’s about our diet Factors Influencing GI 1. 2. 3. 4. 5. Biochemical structure of the carbohydrate Absorption process Size of the food particle Contents and timing of the previous meal Co-ingestion of fat, fiber, or protein Carbohydrates and Weight Loss?? • Low carb diets • ‘Diet’ and low calorie foods http://www.sigmaaldrich.com/img/assets/ 4202/sigma_metabolic_path-new.pdf
