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Carbohydrates: Bountiful Sources of Energy and Nutrients

Carbohydrates: Bountiful Sources of Energy and Nutrients. What Are Carbohydrates?. Carbohydrates One of the three macronutrients A primary energy source, especially for nerve cells Composed of carbon, hydrogen, oxygen Good sources include fruits and vegetables. What Are Carbohydrates?.

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Carbohydrates: Bountiful Sources of Energy and Nutrients

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  1. Carbohydrates:Bountiful Sources of Energy and Nutrients

  2. What Are Carbohydrates? • Carbohydrates • One of the three macronutrients • A primary energy source, especially for nerve cells • Composed of carbon, hydrogen, oxygen • Good sources include fruits and vegetables

  3. What Are Carbohydrates? • Glucose • The most abundant carbohydrate • Produced by plants through photosynthesis

  4. Photosynthesis

  5. What Are Carbohydrates? • Simple carbohydrates • Contain one or two molecules • Monosaccharides contain only one molecule • Glucose, fructose, galactose • Disaccharides contain two molecules • Lactose, maltose, sucrose

  6. Monosaccharides

  7. Disaccharides

  8. What Are Carbohydrates? • Complex carbohydrates • Long chains of glucose molecules • Hundreds to thousands of molecules long • Also called polysaccharides • Starch, glycogen, most fibers

  9. Complex Carbohydrates

  10. Complex Carbohydrates • Starch • Plants store carbohydrates such as starch • We digest (break down) starch to glucose • Grains, legumes, and tubers are good sources of starch in our diet

  11. Complex Carbohydrates • Glycogen • Animals store carbohydrate as glycogen • Stored in the liver and muscles • Not found in food and therefore not a source of dietary carbohydrate

  12. Complex Carbohydrates • Fiber • Dietary fiber is the non-digestible part of plants • Grains, rice, seeds, legumes, fruits • Functional fiber is carbohydrate extracted from plants and added to food • Cellulose, guar gum, pectin, psyllium • Total fiber = dietary + functional fiber

  13. Digestion of Carbohydrates • Salivary amylase • Enzyme that begins carbohydrate digestion in the mouth • Breaks carbohydrates down to maltose • There is no digestion of carbohydrates in the stomach.

  14. Digestion of Carbohydrates

  15. Digestion of Carbohydrates • Most chemical digestion of carbohydrates occurs in the small intestine. • Pancreatic amylase • Enzyme produced in the pancreas and secreted into the small intestine • Digests carbohydrates to maltose

  16. Digestion of Carbohydrates • Additional enzymes in the small intestine digest disaccharides to monosaccharides. • These enzymes include maltase, sucrase, and lactase. • Monosaccharides are absorbed into the cells lining the small intestine and then enter the bloodstream.

  17. Digestion of Carbohydrates • All monosaccharides are converted to glucose by the liver. • Glucose circulating in the blood is our primary energy source. • Excess glucose is converted to glycogen by the liver.

  18. Storage of Glycogen

  19. Digestion of Carbohydrates • We do not have the enzymes necessary to digest fiber. • Bacteria in the large intestine can break down some fiber. • Most fiber remains undigested and is eliminated with feces.

  20. Regulation of Blood Glucose • The level of glucose in the blood must be closely regulated. • Two hormones, insulin and glucagon, control the level of glucose in the blood.

  21. Regulation of Blood Glucose: Insulin • Insulin • Produced by beta cells of the pancreas • Helps cells take in glucose from the blood • Stimulates the liver to take up glucose and convert it to glycogen

  22. Regulation of Blood Glucose: Insulin

  23. Regulation of Blood Glucose: Glucagon • Glucagon • Produced by alpha cells of the pancreas • Stimulates the breakdown of glycogen to glucose to make glucose available to cells of the body • Stimulates gluconeogenesis – the production of glucose from amino acids

  24. Regulation of Blood Glucose: Glucagon

  25. Regulation of Blood Glucose • Glycemic index • A food’s ability to raise blood glucose levels • Foods with a low glycemic index: • Are better for people with diabetes • Are generally higher in fiber • May reduce the risk of heart disease and colon cancer

  26. The Role of Carbohydrates • Energy • Each gram of carbohydrate = 4 kcal • Red blood cells rely only on glucose for their energy supply • Both carbohydrates and fats supply energy for daily activities • Glucose is especially important for energy during exercise

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