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Soluble Fiber • examples include gums, pectins, some hemicelluloses • functions: – delay gastric emptying – slow transit through the digestive system – delay glucose absorption – bind to bile, help decrease cholesterol • food sources: fruits 1 Insoluble Fiber • examples include cellulose, hemicellulose • functions: – – – – speed transit through the digestive tract delay glucose absorption soften stool to ease passage reduces risk of hemorrhoids((البواسير, diverticulitis ((االنسداداتand appendicitis()التهابات الزائدة الدودية • food sources: cereal grains, legumes, vegetables, nuts 2 DERIVED CARBOHYRATES Oxidation Products Gluconic acid Reduction Products Amino Sugars Deoxy Sugars Glycerol Glucosamine Glucuronic acid Ribitol Galactoseamine Glucaric acid Mannoseamine Deoxyribose “These are derived from carbohydrates by various chemical reactions” Oxidation products These reactions produce different products according to the reagent used. i-Bromine water; is a mild oxidizing reagent. It selectively oxidizes the -CHO group into -COOH, and converts aldoses to the corresponding aldonic acids ii-Nitric acid; is a strong oxidizing agent. It oxidizes both the -CHO and terminal -CH2OH of an aldose to COOH groups, and these dicarboxylic acids are known as aldaric acids. CHO H HO CHO COOH OH H H Br2/H2O HO OH H H HO COOH OH H H HNO3 OH HO H H OH H OH H OH H OH H OH H OH H OH H OH CH2OH Glucose CH2OH Gluconic acid CH2OH Glucose COOH Glucaric acid iii-Controlled oxidation: this is carried out by first protecting the -CHO group, followed by oxidation of the -CH2OH group to give alduronic acid, e.g. oxidation of glucose into glucuronic acid. Reduction product Aldoses and ketoses can be reduced with sodium borohydride into the corresponding alditols. Examples: glucose gives sorbitol (-CHO is converted to –OH), mannose gives mannitol, galactose gives dulcitol. 6 This reduction occure under hydrogen gas at aspecific pressure and presence of Na/Hg as Chemical catalyst or sodium borohydride (NaBH4 ). 7 Substitution products (Amino sugars) • It is occur by specialized enzymes •Where the replacement of a hydroxyl group in one of the following groups: •NH2 •CH3 •R-CO Example: Replacing the hydroxyl group on the second carbon atom in the glucose group with amine group and produces a compound of glucose amine. This compound is important for formation of glycoprotein. 8 9 Regulation of Blood Glucose Optimal functioning of the body is dependant on keeping levels of glucose within certain parameters. Elevated blood glucose = Hyperglycemia Low blood glucose = Hypoglycemia The ENDOCRINE SYSTEM is primarily responsible for regulating blood glucose. The two main hormones are INSULIN and GLUCAGON. 10 Regulation of Blood Glucose 11 Glucose —The most important carbohydrate Function : • Glucose can be converted into • glycogen • ribose • galactose • Glycoproteins — molecular targeting • Antibodies and blood clotting factors((عوامل تخثر الدم • Structural components of cell membranes Diseases associated with carbohydrates • Diabetes mellitus • Galactosemia • Lactose intolerance • Glycogen storage diseases 12 Diabetes Mellitus • a disorder of energy metabolism due to failure of insulin to regulate blood glucose • results in hyperglycemia • acute symptoms include thirst, increased urine production, hunger • long term consequences include increased risk of heart disease, kidney disease, blindness()فقد البصر, neural damage • two forms: Type I and Type II 13 Diabetes Mellitus Type I • accounts for about 10% of cases • occurs when b cells of the pancreas are destroyed – insulin cannot be synthesized • without insulin, blood glucose levels rise because the tissues are unable to access the glucose • death occurs shortly after onset unless given injections of insulin 14 Diabetes Mellitus Type II • occurs when cells of body are unable to respond to insulin • called “insulin insensitivity” or “insulin resistance” • blood glucose levels rise • insulin secretion increases in an attempt to compensate – leads to hyperinsulinemia()فرط افراز األنسولين 15 Hypoglycemia • dramatic drop in blood glucose • symptoms similar to an anxiety attack: rapid weak heart beat(زيادة معدل ضربات القلب, sweating((تعرق, anxiety((قلق, hunger((جوع, trembling((ارتجاف, weakness()ضعف • RARE in healthy people • may occur as a result of poorly managed Diabetes or other causes: – reactive hypoglycemia – fasting hypoglycemia 16 The Glycemic Index • a measure of the extent to which a food raises blood glucose concentration & elicits an insulin response compared to pure glucose Low pasta baked beans bran cereals apples milk Moderate banana orange juice ice cream High white bread cornflakes potatoes jelly beans watermelon 17 The Glycemic Index cont. Glucose Baked potato Jelly bean Honey Bagel Sucrose Boiled new potato Brown rice Chocolate Boiled carrots Orange Spaghetti Apple Skim milk Lentils Fructose 100 85 78 73 72 65 62 55 49 47 44 42 38 32 29 23 18 The Glycemic Index cont. The Theory… • consuming foods with a low glycemic index will minimize dramatic fluctuations in blood glucose • this reduces the need for insulin secretion and may help manage Type II Diabetes • eating several small meals frequently has similar metabolic effects on blood glucose as does consuming low glycemic index foods 19