The Carbohydrates Sugars Starches and Fibers Chapter 4 Lecture 1 Dr Alisha Rovner University of Delaware Nutrition Concepts NTDT200 Fall 2013 Class overview Carbohydrate review Chemistry review Carbohydrate structure Class Objectives Explain what a carbohydrate is and what food sources of carbohydrates are Understand the chemical structure of carbohydrates Identify the monosaccharides disaccharides and polysaccharides common in nutrition and their major food sources Carbohydrate Review Macronutrient that provides 4 kcal g All plant foods whole grains vegetables legumes fruits provide ample carbohydrates Acceptable Macronutrient Distribution Range AMDR for adults Carbohydrates 45 65 of kcal Fat 20 35 of kcal Proteins 10 35 of kcal 4 main types of atoms in nutrients Carbon C Nitrogen N Oxygen O Hydrogen H Atoms and Their Bonds Each atom can form a certain number of chemical bonds with other atoms Carbon atoms 4 Nitrogen atoms 3 Oxygen atoms 2 Hydrogen atoms 1 Atoms and Their Bonds Bonds are represented as lines between the chemical symbols Structure of Carbohydrates Composed of carbon hydrogen and oxygen Arranged as monosaccharides single sugars or multiple disaccharides Most carbohydrates have a ratio of one carbon molecule to one water molecule carbo carbon C hydrate with water H2O Dietary Carbohydrate Family Monosaccharides Most basic units of carbohydrates All have same and kinds of atoms but in different arrangements Disaccharides Pairs of monosaccharides linked together Polysaccharides Contain many glucose units and in some cases monosaccharides strung together Dietary Carbohydrates Monosaccharides and disaccharides sugars are sometimes called simple carbohydrates Polysaccharides starches and fibers are sometimes called complex carbohydrates Carbohydrate Family Monosaccharides single sugars Glucose aka blood sugar Fructose aka fruit sugar Sweetest of sugars Galactose Found in very few foods Glucose blood sugar Serves as an essential energy source for all the body s activities People don t eat glucose directly When carbohydrate rich foods are eaten the body receives glucose for immediate energy and converts some into glycogen for reserve energy Fructose fruit sugar Sweetest of the sugar Occurs naturally in fruits and honey Soft drinks ready to eat cereals and desserts have been sweetened with high fructose corn syrup Galactose Occurs naturally in only a few foods Found in milk Galactosemia is a rare genetic disorder in which the body is unable to metabolize galactose Treatment requires the strict exclusion of lactose galactose from the diet The Monosaccharides All have same and kinds of atoms but in different arrangements Carbohydrate Family Disaccharides sugars composed of pairs of monosaccharides Maltose glucose glucose Sucrose glucose fructose Lactose glucose galactose All contain glucose Maltose Two glucose units Produced whenever starch breaks down Occurs during the fermentation process that yields alcohol Only in a few foods including barley Sucrose Fructose glucose Commonly known as table sugar Also occurs in many fruits and some vegetables and grains Lactose Galactose glucose Principal carbohydrate of milk Known as milk sugar Carbohydrate Family Polysaccharides More complex than monosaccharides and disaccharides Contain many glucose units Three types important in nutrition Glycogen Starches Fibers Glycogen Animal polysaccharide composed of glucose When people eat carbohydrate rich foods their bodies receive glucose for immediate energy and convert some glucose into glycogen for reserve energy Starches Humans store glucose as glycogen and plant cells store glucose as starches Long branched or unbranched chains of hundreds or thousands of glucose molecules linked together When a person eats plants the body hydrolyzes starch into glucose for energy Figure 4 6b p99 Dietary Fiber Structural parts of plants found in all plant derived foods 2 types of fiber Soluble found in oats barley legumes Associated with lowering blood cholesterol and glucose Insoluble found in whole grains Promotes bowel movements and alleviates constipation Table 4 1 p101
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