NUTRITION EXAM 2

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carbohydrates

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Terms in this set (27)

compounds composed of carbon, oxygen, and hydrogen arranged as monosaccharides or multiple monosaccharides; most but not all carbohydrates have a ratio of one carbon molecule to one water molecule

monosaccharides

single sugar, simple carbohydrates

glucose

a monosaccharide; a larger and more complicated molecule than the ethyl alcohol

each atom has 4 bonds, each oxygen has 2 bonds, and each hydrogen has 1 bond

is one of the two sugars in every disaccharide and the unit from which the poly saccharides are made almost exclusively

starch

storage form of energy in plants; long, branched or unbranched chains of hundreds or thousands of glucose molecules linked together; giant starch molecules are packed side by side in wheat, rice, yams, potatoes, peas, and beans; after being eaten, the body hydrolyzes the starch to glucose and uses the glucose for its own energy purposes; all starchy foods come from plants; grains are the richest source of starch

glycogen

polysaccharide; an important storage form of energy in the body; found in some meats & plants; food is not significant source of glycogen; made of many glucose molecules linked together in highly branched chains

fructose

monosaccharide, the sweetest of the sugars; has the same exact formula as glucose: C6H12O6

occurs naturally in fruits and honey; added into soft drinks, cereals, & desserts

disaccharides

sugars composed of pairs of monosaccharides; simple carbohydrates

condensation

a chemical reaction that links two monosaccharides together; water is released as two molecules combine to form one larger product

hydrolysis

this occurs to break a disaccharide in two; a molecule of water splits to provide the H and OH needed to complete the resulting monosaccharides; common during digestion

maltose

produced whenever starch breaks down--during carbohydrate digestion; occurs during the fermentation process that yields alcohol

sucrosedisaccharide; formed by fructose & glucose; the sweetest of the disaccharides because it contains fructoselactosedisaccharide; combination of galactose and glucose; this is the principal carbohydrate of milk; known as milk sugar, lactose contributes to half of the energy (kcalories) provided by fat-free milkpolysaccharideslarge molecules composed of chains of monosaccharidescomplex carbohydratescompounds composed of many monosaccharides linked togetherfibersprovide structures in steams, trunks, roots, leaves, and skins of plants; pass through the body undigested, so they contribute no monosaccharides, and little or no energy; some dietary fibers dissolve in water (soluble fibers), form gels (viscous), and are easily digested by bacteria in colon (fermentable) soluble - found in oats, barley, legumes, and citrus fruits; soluble fibers are associated with protecting against heart disease and diabetes by lowering blood cholesterol and glucose levels insoluble - found in whole grains (bran) and vegetables; promote bowel movements, alleviate constipation, and prevent diverticular diseaseresistant starchesstarches escape digestion and absorption in the small intestine whole or partially milled grains, legumes, and just-ripened bananas, and chilled cooked potatoes, pasta, and ricephytic acidnot a dietary fiber, but it is often found in fiber-rich foods; because of this close association, researchers have been unable to determine whether it is the dietary fiber, the phytic acid, or both that binds with minerals preventing their absorptiondigestion of carbohydrateswhen a person eats food containing starch, enzymes hydrolyze the long chains to shorter chains, the short chains to disaccharides, and disaccharides to monosaccharidesStep 1 of Carbohydrate DigestionMouth chews high-fiber foods, slows eating, and stimulates the flow of saliva; salivary enzyme amylase starts to work, hydrolyzing starch to shorter polysaccharides to disaccharide maltoseStep 2 of Carbohydrate DigestionStomach carbohydrate digestion ceases here; the activity of salivary amylase diminishes as the stomach's acid and protein-digesting enzymes deactivate the enzyme; stomach digestive juice contain no enzymes to break down carbohydrates; fiber is NOT DIGESTED but because they linger in the stomach they provide satiety: feeling of fullness and satisfactionStep 3 of Carbohydrate Digestionin the small intestine performs most of the work of CHO digestion; pancreatic amylase enters the intestine via the pancreatic duct and continues to break down the polysaccharides to shorter glucose chains and maltose; final steps take place on the outer membranes of the intestinal cells; at this point, all polysaccharides and disaccharides have been broken down to monosaccharides (mostly glucose)maltasebreaks down maltose into 2 glucosesucrasebreaks down sucrose into 1 glucose and 1 fructoselactasebreaks down lactose into 1 glucose and 1 galactoseStep 4 of Carbohydrate Digestionlarge intestine within 1-4 hours after a meal, all the sugars and most of the starches have been digested; only fiber remain; fibers in the large intestine attract water, which soften the stool for passage without strainingcarbohydrate absorptionnutrient absorption takes place in the small intestine; glucose and galactose enter the cells lining the small intestine by active transport, fructose is absorbed by facilitated diffusionintoleranceintestinal cells produce enough of the enzyme lactase to ensure that the disaccharide lactose found in milk is both digested and absorbed efficiently