Human Nutrition 2310 Exam 2 Chapter 5 Carbohydrates Composed of Carbon Hydrogen and Oxygen General Chemical Formula CH2O n Simple Forms o Only contain 1 or 2 sugar units o Monosaccharides Simplest form of carbohydrate Contain 6 carbon 12 hydrogen and 6 oxygen molecules but in a slightly different configuration Classification as hexoses because have 6 carbon molecules Glucose Most abundant monosaccharide Usually lined with other monosaccharides Also called dextrose Fructose Found in fruits vegetables honey high fructose corn syrup High fructose corn syrup less expensive than sucrose used in many food products Also called levulose Galactose In the diet is usually linked with glucose to form lactose Sugar Alcohols Derivatives of monosaccharides Used as sweeteners in gum dietetic foods o Sorbitol o Mannitol o Xylitol Pentoses 5 carbon sugars o Ribose RNA o Deoxyribose DNA o Disaccharides Contain 2 monosaccharides linked together in a condensation reaction which forms 1 molecule of water Alpha Bonds o Found in maltose and sucrose o Easily broken down by intestinal enzymes Beta Bonds o Found in lactose and dietary fiber o Not easily broken down by intestinal enzymes Glucose glucose Found in malted alcoholic beverages Formed in small intestine from digestion of longer chain polysaccharides Maltose Sucrose Glucose fructose Lactose Found in plants such as sugar cane sugar beets maple tree sap Brown white and powdered sugars are produced from plant sources Glucose Galactose Found in milk and milk products Lactose intolerance results from insufficient lactase production o Lactase needed to break beta bonds leads to intestinal gas bloating cramping and discomfort when undigested lactose is metabolized into acids and gases by colonic bacteria Complex carbohydrates that contain 3 to 10 simple sugar units Cannot be digested by human enzymes but are metabolized by colonic bacteria and produce intestinal gas Enzyme preparations e g Beano break down oligosaccharides before reach large intestine Examples Raffinose o Indigestible oligosaccharide made of 3 monosaccharides galactose glucose fructose Stachyose o Indigestible oligosaccharide made of 4 monosaccharides galactose galactose glucose fructose o Both are found in onions cabbage broccoli whole wheat and legumes e g kidney beans soybeans Complex Forms o Oligosaccharides o Polysaccharides Complex carbohydrates with many glucose molecules Digestibility determined by type of bonds alpha or beta Starch Major digestible dietary polysaccharide Cooking increases digestibility of starches by making them soluble in water Storage form of glucose in plants two types amylose amylopectin Amylose o Straight chain of many glucose molecules linked by alpha 1 4 bonds that are broken by amylase produced in mouth and pancreas o Modified food starch made by bonding amylose rich molecules together used as a thickening agent in foods such as salad dressings instant pudding Amylopectin o Branched chain of many glucose molecules linked by alpha 1 6 bonds that are broken by intestinal enzyme alpha dextrinase plus straight chains with alpha 1 4 bonds broken by amylase o Causes more rapid rise in blood glucose than amylose because are more sites for enzyme action o Retains water to form stable starch gel used to thicken sauces Glycogen and gravies Storage form of carbohydrate in humans and animals Glucose units linked by alpha bonds More highly branched than amylopectin broken down quickly Stored in liver and muscle cells amount influenced by dietary intake o Liver glycogen maintains blood glucose levels muscle glycogen supplies glucose to muscle during exercise o Plants are the main source of carbohydrates Plants produce glucose by photosynthesis from carbon air oxygen air hydrogen water and energy sun Plants either store glucose or transform it into starch fiber fat or protein Storage form of glucose in body what it is where it is located how linked together o Glucose circulates from liver to body cells where it is used for energy If blood glucose levels adequate glucose stored as glycogen in liver or muscle If glycogen storage capacity exceeded glucose converted to fat for storage in adipose tissue Function of carbohydrates o Provide Energy o Spare protein as an energy source o Prevent ketosis Benefits of dietary fiber both soluble and insoluble o Soluble Fibers aka viscous fibers Lower blood cholesterol Dissolve in water become gel like Metabolized by colonic bacteria Delay gastric emptying Lower blood glucose Reduced risk of CVD and diabetes Examples Gums and mucilages legumes seaweed psyllium Pectins fruits Some hemicelluloses oat bran o Insoluble Fibers Not easily dissolved in water Not easily metabolized by colonic bacteria Decrease intestinal transit time Reduce constipation diverticular disease colon cancer Examples Hemicelluloses whole grains some vegetables Lignins seeds of fruits bran layer Cellulose skin of fruits and vegetables legumes celery whole grain Types of bonds in carbohydrates they affect digestibility what they are in which carbohydrates they are found how o Digestibility determined by type of bonds alpha or beta Alpha Bonds Easily broken down by intestinal bonds Beta Bonds Not easily broken down by intestinal enzymes Maltose Sucrose Glucose Lactose and Dietary Fiber Use of carbohydrates in food processing manufacturing what kinds used and for what o Nutritive Sweeteners Simple Sugars monosaccharaides and disaccharides High Fructose Corn Syrup Similar to sucrose in sweetness but less expensive Sugar Alcohols 1 5 3 kcal gram Often used in sugarless gum and candies May cause diarrhea in large quantities Ex Sorbitol Mannitol and Xylitol o Non nutritive alternative sweeteners Non caloric or very low calorie sugar substitutes for diabetes or weight loss Examples saccharin aspartame neotame acesulfame K sucralose tagatose stevia PKU foods and ingredients to avoid o Phenylketonuria PKU disease that interferes with phenylalanine metabolism o AVOID Aspartame NutriSweet Equal Health risks from extremely high fiber diets o Fiber intakes 50 60 g d especially combined with low fluid intake can result in hard Can lead to painful elimination hemorrhoids rectal bleeding or intestinal blockages o May decrease absorption of some minerals e g zinc iron o May lead to inadequate calorie consumption in children elderly and malnourished dry stools individuals High fiber intakes may cause a sense of fullness and reduce food intake Diabetes types incidence causes