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Carbohydrates

Carbohydrates . Part One: A. Classification B. Digestion & Absorption of CHO. Carbohydrate Is Made by Photosynthesis. CHO. Carbohydrate Classifications. Simple CHO = “Sugars” Monosaccharides: single sugar unit Disaccharides: two sugar units linked together

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Carbohydrates

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  1. Carbohydrates Part One: A. Classification B. Digestion & Absorption of CHO

  2. Carbohydrate Is Made by Photosynthesis CHO

  3. Carbohydrate Classifications • Simple CHO = “Sugars” • Monosaccharides: single sugar unit • Disaccharides: two sugar units linked together • Complex CHO= Starch, glycogen, fiber • Polysaccharides: many sugar units linked together

  4. Simple CHO: Sugars • Monosaccharides • Disaccharides

  5. condensation hydrolysis

  6. Simple Sugars, Cont. • What is sugar good for? • When is sugar considered to be “bad?”

  7. 10% recommendation • (current U.S. 24%) • high sugar diet can change in fat distribution toward central adiposity • binge trigger in some, inhibitor in others – highly individual

  8. fructose/levulose glucose/dextrose honey/invert sugar fruit juice concentrate corn syrup corn sweetener molasses raw sugar turbinado sugar Sugar on the Food Label

  9. Sugar Alcohols • E.g. mannitol, sorbitol, xylitol • Considered “sugar free” sweeteners, but still almost the same kcals as sugar • Sugar free candy -- diarrhea if eaten in excess

  10. A word about lactose: milk sugarand lactose intolerance • Enzyme lactase splits lactose into glu-gal in the small intestine • Lactase deficiency causes trouble digesting milk products

  11. Different from milk allergy, immune rx to casein

  12. Carbohydrate Classifications • Simple CHO = “Sugars” • Monosaccharides: single sugar unit • Disaccharides: two sugar units linked together • Complex CHO= Starch, glycogen, fiber • Polysaccharides: many sugar units linked together

  13. Complex CHO: Polysaccharides:Several to Hundreds of ____________ Units Linked Together • Starch – • Glycogen – • Fiber –

  14. Starch • Long straight or branched chains of hundreds of __________________ units • Sources: • Richest source: • Legumes • Tubers

  15. When eaten, ALL starches are broken down enzymatically to ______________ • (blue dots!) • One to 4 hours after a meal, all starch __________________

  16. Glycogen • Storage form of CHO in animals. Not found in diet. • More complex and more highly branched than starch • Limitedcapacity for storage

  17. Muscle Glycogen • Liver Glycogen

  18. Fiber • Typical U.S. diet: • Most fibers are polysaccharides but

  19. Most common fibers: cellulose, hemicellulose, and pectin. Also gums, mucilages, and lignins • Sources:

  20. Whole Vs. Refined Grains • Whole grains • Label:

  21. Refined grains • Label: • Sources:

  22. “Enriched” • When bran and germ are removed, several vitamins/minerals also • “enriched,” • Shoot for at least half of your grains to be from whole grain sources

  23. Soluble vs. Insoluble fiber • Soluble fiber • foods: barley, fruits (apples), legumes, oats, oat bran, rye, seeds, vegetables, nuts • Health benefits: • lowers serum cholesterol • stool bulk/softening

  24. Insoluble fiber • Foods: brown rice/whole grains/wheat bran, fruits, legumes, seeds, veggies • Health benefits: • Speeds transit through intestines • delayed starch hydrolysis: slowed glu absorption

  25. If you have a low-fiber diet, add fiber gradually! • What about fiber supplements?

  26. Carbohydrates Digestion and absorption of CHO

  27. Dietary CHO = starch, sugar, and fiber

  28. D&A of CHO • Mouth Salivary amylase starch dextrins & maltose glu-glu-glu-glu-glu-glu glu-glu-glu-glu-glu-glu-glu-glu-glu x100 glu-glu

  29. Stomach • Mechanical digestion continues in stomach, but

  30. Small Intestine Starch and dextrins Pancreatic amylase maltose glu-glu glu-glu-glu-glu-glu-glu

  31. Last phase: The brushborder cells of the small intestine. • Enzymes in these cells break down ___________________ to _____________________. (maltase) maltose glu & ________ (lactase) lactose glu & ________ (sucrase) glu & ________ sucrose

  32. Monosaccharides are ABSORBED • In liver, fru and gal are converted to glu • ____________ then regulates the release of glu back into the bloodstream for transport to tissues.

  33. Large Intestine (colon) • Fiber  • (absorbed & used for E, 0-2kcals/g of fiber) • (Cellulose and lignin completely pass through in feces)

  34. So now we have glucose in the liver and the bloodstream. If glu is to fuel the tissues, how is it done? • “Glucose-dependent tissues” rely on glucose for fuel (not fat) • Brain, nervous system, retina, etc. • ***

  35. Average person enough CHO stored to last ________________ hours • Since we can’t store much, need to rely on dietary CHO.

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