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Human Nutrition 2310 - Exam 2Chapter 5: Carbohydrates  Composed of Carbon, Hydrogen, and Oxygen General Chemical Formula = (CH2O)nSimple Formso Only contain 1 or 2 sugar unitso 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 foodproducts- 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 foodso Sorbitolo Mannitolo Xylitol Pentoses - 5 carbon sugarso Ribose (RNA)o Deoxyribose (DNA)o Disaccharides  Contain 2 monosaccharides linked together in a condensation reaction, which forms 1 molecule of water- Alpha Bondso Found in maltose and sucroseo Easily broken down by intestinal enzymes- Beta Bondso Found in lactose and dietary fibero Not easily broken down by intestinal enzymes Maltose - Glucose + glucose - Found in malted alcoholic beverages - Formed in small intestine from digestion of longer-chain polysaccharides  Sucrose - Glucose + fructose - Found in plants such as sugar cane, sugar beets, maple tree sap - Brown, white, and powdered sugars are produced from plant sources  Lactose - 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 Formso Oligosaccharides 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)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 and gravies  Glycogen - 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 Energyo Spare protein as an energy sourceo Prevent ketosis Benefits of dietary fiber (both soluble and insoluble) o Soluble Fibers (aka viscous fibers) Dissolve in water – become gel-like Metabolized by colonic bacteria Lower blood cholesterol Delay gastric emptying Lower blood glucose Reduced risk of CVD and diabetes Examples:- Pectins (fruits)- Some hemicelluloses (oat bran)- Gums and mucilages (legumes, seaweed, psyllium)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:- Cellulose (skin of fruits and vegetables, legumes, celery, whole grain)- Hemicelluloses (whole grains, some vegetables)- Lignins (seeds of fruits, bran layer) Types of bonds in carbohydrates – what they are, in which carbohydrates they are found, how they affect digestibility o Digestibility determined by type of bonds (alpha or beta) Alpha Bonds = Easily broken down by intestinal bonds- Maltose, Sucrose, Glucose Beta Bonds = Not easily broken down by intestinal enzymes- 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 Xylitolo 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 metabolismo AVOID: Aspartame (NutriSweet, Equal) Health risks from extremely high fiber diets o


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OSU HUMNNTR 2310 - Chapter 5: Carbohydrates

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