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Chapter 4: Carbohydrates

Chapter 4: Carbohydrates. Plants Synthesize Glucose. Simple Sugars. Monosaccharides Single sugar molecules Disaccharides Pairs of monosaccharides . Glucose Fructose Galactose. Monosaccharides. Glucose (Dextrose). Not used as a sweetener Source: breakdown of starch and other sugars.

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Chapter 4: Carbohydrates

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  1. Chapter 4: Carbohydrates

  2. Plants Synthesize Glucose

  3. Simple Sugars • Monosaccharides • Single sugar molecules • Disaccharides • Pairs of monosaccharides

  4. Glucose Fructose Galactose Monosaccharides

  5. Glucose (Dextrose) • Not used as a sweetener • Source: breakdown of starch and other sugars

  6. Glucose in the Body • Form of sugar found in the blood • Only energy source for the brain • Quick energy for muscles

  7. Fructose (fruit sugar) • Sweetest monosaccharide • Metabolized to glucose in the liver • Found in fruit, honey, and high fructose corn syrup • Is in sucrose (table sugar)

  8. Galactose • Not used as sweetener • Usually bound with glucose (lactose or milk sugar) • Converted to glucose in the liver • Available fuel source

  9. Disaccharides: Pairs of Sugars • “Simple sugars” • Linked monosaccharides • Always contain glucose

  10. Sucrose • Glucose + Fructose • Table sugar • Soft drinks, candy, ice cream • Baked goods, jelly, cereal

  11. Lactose • Galactose + Glucose • Dairy products • Increases calcium absorption

  12. Maltose (malt sugar) • Glucose + Glucose • Sprouting seeds • Digestion of starch • Fermentation • Alcohol production

  13. Complex Carbohydrates Polysaccharides: Starch & Glycogen • Amylose: straight chain digestible starch • Amylopectin: branched chain digestible starch • Dietary fiber: non-digestible

  14. Oligosaccharides • 3-10 monosaccharides • Found in beans and legumes • Not digested • Metabolized by bacteria in the large intestine • Beano®

  15. Polysaccharides: Starch • 3,000 or more monosaccharides bound together • Plant storage of glucose • Two forms • Amylose--straight chain polymer • Amylopectin--highly branched polymer

  16. Polysacchai\rides

  17. Sources of Starch • Grain products: bread, cereal, pasta • Some “starchy” vegetables: corn, peas, carrots, potatoes

  18. Glycogen • Storage form of CHO for animals and human • Structure similar to amylopectin • More sites for enzyme action • Found in the liver and muscles

  19. Glycogen Sources • Dietary: insignificant • Made in the body • Stored in the liver and muscles

  20. Dietary Fiber • Plant cells • Cannot be digested by humans • Humans lack necessary enzymes to break the bonds

  21. Dietary Fiber Found only in plants • Whole grains • Fruits • Vegetables

  22. Types of Fiber Insoluble fiber • Cellulose, hemicellulose, lignin • Does not dissolve in water • Not fermented by bacteria in the colon • Tough, fibrous parts of vegetables • Cereal bran, whole grains, fruit

  23. Types of Fiber Soluble fiber • Gum, Pectin, Mucilage • Fermented in colon • Sources: Fruits, vegetables, oats, beans, rice bran, psyllium seed

  24. Soluble and Insoluble Fiber

  25. Health Benefits of Insoluble Fiber • Decreases intestinal transit time • Promotes regularity, softer stools • Reduces constipation • Reduces risk of hemorrhoids (varicose veins in the rectum) caused by constipation

  26. Health Benefits of Insoluble Fiber • Reduces risk of diverticulosis • Outpouching of intestinal wall • Diverticulitis: inflamed pouches • High fruit and vegetable intake seems to reduce risk of colon cancer, though fiber may not be the factor

  27. Diverticula

  28. Health Benefits of Soluble Fiber • Associated with reduced risk of cardiovascular disease • Slows absorption of glucose from the small intestine • Appears to reduce risk of diabetes • May help with blood glucose control (but requires very large amounts of fiber)

  29. Health Benefits of All Fiber Weight management • Bulky, high-fiber foods fill you up • Have low energy density • May reduce risk of obesity

  30. Negative Effect of Excessive Fiber • >60 g/day • Bind minerals (calcium, zinc, iron) • Satiety without adequate nutrients, especially in children • Diarrhea • Constipation: if inadequate water can result in bowel obstruction

  31. CHO in Food

  32. Carbohydrate Digestion

  33. Effects of Cooking • Softens fibrous tissues • Easier to chew and swallow

  34. Digestion of Carbohydrate in the Mouth • Saliva contains amylase • Starch is broken down to shorter saccharides • Taste the sweetness with prolong chewing • Proceeds down the esophagus

  35. Digestion of Carbohydrate in the Stomach • The acidic environment stops the action of salivary amylase • No further starch digestion occurs

  36. In the Small Intestine • Pancreatic amylase is released • Intestinal cells release enzymes Maltose + maltase glucose + glucose Sucrose + sucrase glucose + fructose Lactose + lactase glucose + galactose • Monosaccharides are absorbed

  37. Lactose Intolerance • Reduction in lactase • Lactose is undigested and not absorbed • Lactose is metabolized by large intestinal bacteria • causes gas, bloating, cramping, discomfort • Primary lactose intolerance disease • Secondary lactose intolerance disease

  38. What To Do If You Are Lactose Intolerant • Determine amount you can tolerate • Eat dairy with fat • Cheese & yogurt are usually tolerated well • Use of Lact-Aid

  39. CHO Digestion

  40. CHO Absorption Glucose and Galactose • Active absorption • Energy is expended • Going from low to high concentration gradient Fructose • Facilitated diffusion using a carrier • No energy expended

  41. Portal Vein • Transport absorbed monosaccarhides • Delivers them to the liver Liver can: • transform fructose/galactose into glucose • release them into the blood stream • store as gylcogen (or fat)

  42. Uses of Glucose Energy • Brain’s only source • Muscle – quick energy Glycogen • Muscle: used by individual muscle • Liver: maintain blood sugar Excess converted to fat • Stored in fat cells • Future energy use as fat

  43. Regulation of Blood Glucose • Hyperglycemia • Hormone regulates • Insulin • Hypoglycemia • Hormones regulate • Glucagon • Epinephrine

  44. Blood Glucose Control • Role of the liver • Regulates glucose that enters bloodstream • Role of the pancreas • Release of insulin • Release of glucagon

  45. Functions of Insulin • Promotes glycogen synthesis • Increases glucose uptake by the cells • Reduces gluconeogenesis • Net effect: lowers the blood glucose

  46. Functions of Glucagon • Breakdown of glycogen • Enhances gluconeogenesis • Net effect: raises blood glucose

  47. Epinephrine/ Norepinephrine • “fight or flight” response • breakdown glycogen • raises blood glucose

  48. Diabetes Mellitus-Type 1 • Genetic link • Immunological disorder • Associated with early introduction of cow’s milk • Absence of insulin • Insulin dependent • Hyperglycemia

  49. Treatment for Type 1 • CHO counting • Insulin therapy • Risk for heart disease, kidney damage, other complications

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