Chapter 6: Carbohydrates Define the following terms. • • • added sugars—sugars extracted from plants and used to sweeten foods. carbohydrates—nutrient that is a person’s main source of energy; found mostly in plant foods. chlorophyll—green pigment in plants; must be present for photosynthesis to occur. complex carbohydrates— carbohydrates with complicated structures; starches. • • • dietary fiber—plant materials that are eaten but can’t be digested by human enzymes. disaccharides—form when two monosaccharides (single sugars) combine chemically. monosaccharides—sugars with singleunit chemical structure. photosynthesis—chemical process by which plants make carbohydrates. • • • polysaccharides—complicated chemical arrangements that plants form by combining single glucose units to build starches. simple carbohydrates—sugars formed from simple one- and two-unit structures. starches—formed when plants combine single glucose units into more complicated chemical structures. • • sugars—simple carbohydrates chemically formed from plants; made of carbon, hydrogen, and oxygen. sugar substitutes—artificial sweeteners and sugar alcohols are Answer the following questions. • • • • What kinds of foods provide carbohydrates? Some are in milk; most are in plant foods, including fruits, vegetables, grain products, dry beans, nuts, and seeds. Describe photosynthesis. Using the sun’s energy, plants convert carbon dioxide and water into oxygen and the sugar glucose. What makes glucose and sucrose different? • • • Glucose is a monosaccharide, which has a one-unit chemical structure. Sucrose is a disaccharide, which has a two-unit chemical structure. If you saw the word dextrose on a food label, what would you know about that particular ingredient? Why? You would know it is a sugar because it ends in-ose. What is the difference between sugars and starches? • • • Because their one- and two- unit structures are chemically simple, sugars are called simple carbohydrates. Starches combine single glucose units into more complicated chemical structures and are called complex carbohydrates. Why isn’t dietary fiber a nutrient? Because it cannot be digested by human enzymes A teen had a long bike ride coming up the next day, so he decided to get ready by eating a big steak the night before. • Explain you opinion of his decision. • Since energy-producing glucose is only available through plant foods, the steak won’t help. • During digestion, what happens to the carbohydrates you have eaten? • Most are converted back to glucose. Fiber passes through the system undigested. How is the sugar in an apple different from the sugar in a cookie? • • • The apple has naturally occurring sugars. The cookie has added sugar put there for sweetening. 10. Since sugars are used to make starch in a plant, why don’t such starchy foods as potatoes taste sweet? The starch molecules are too large to fit the taste buds receptors Predict what might happen if a person eliminated all carbohydrates from his or her diet. • Eliminating all carbohydrates would disrupt many body processes and make the person have less energy. • Why might a lack of glycogen be a problem? • Glycogen is extra glucose that has been stored for times when the body needs extra energy. If it’s not available, the body will use protein for energy, taking it away from building and repairing tissues. • • A friend says to you: “I’m supposed to cut down on carbohydrates, so I don’t eat many starchy foods now.” Thinking of health, how might you respond? This is not a good idea because health experts suggest that your daily carbohydrate allowance come mostly from complex carbohydrates and naturally occurring sugars rather than added sugars. • • If someone on a 2,000-calorie diet drinks a 12-ounce soft drink, how much more sugar could the person eat during the day if following USDA suggestions? None; the drink probably has about 10 teaspoons of sugar, which is the daily limit suggested fro a 2,000-calorie diet. Suppose a cereal bar haws 16 g of sugar. How many teaspoons of sugar is that? • 4 teaspoons ( 16 divided by 4) • How can a food that replaces sugar with a sugar substitute be high in calories? • It would still be high in calories if it’s high in fat, which has 9 calories per gram. • • Why do some people think that starchy foods make people gain weight? Because they are often eaten with high fat spreads, sauces, and gravies. If fiber is just eliminated as waste, why is it needed? • • • • • • Fiber: absorbs water and helps food move through the large intestine at a normal rate; promotes regular bowel movements; helps prevent constipation; may help reduce cholesterol; adds to feeling of fullness when eating. What kinds of foods contribute fiber to the diet? – Whole-grain foods; – Dry beans. peas, and lentils; – Cooked vegetables.