Carbohydrates-1

1. Carbohydrates-1 Lect-2 Sara AL-Mosharruf

2. objectives • Introduction • Carbohydrates classification • Carbohydrate sources lect-2 • Recommended intakes of carbohydrates • Function of carbohydrate • Digestion , absorption and lect-3 metabolism of carbohydrate • Glucose in the body

3. Introduction • Carbohydrates play a major role in our life and make us healthy. • Every cells of human body needs energy to do its work. • People don't eat glucose directly, they eat carbohydrates. • Then their bodies convert the carbohydrates into glucose for energy and to glycogen for reserve energy. • Dietary carbohydrate provided the body's great source of fuel for energy.

4. The carbohydrates are compounds made of carbon (C), oxygen (O) and hydrogen (H). • These atoms can formspecified number of chemical bonds, carbon form four bonds, oxygen formstwo and hydrogen forms one. C

5. Carbohydrates classification

7. Monosaccharide • Most of the monosaccharides important in nutrition are hexoses. • Monosaccharidesare the simplest form of carbohydrate that can not broke down to smaller units. • The three monosaccharides are important in nutrition, all have the same number and kinds of atoms(C6H12O6), but in different arrangement.

8. The three kinds of monosaccharaides have a different sweetness. Glucose on the tongue gives a mildly sweet, Galactose hardly tastes sweet at all, but Fructose is intensely sweet.

9. Glucose • The basic single sugar in body metabolism is glucose . • Supply the primary fuel for cells . • It is not usually found as such in the diet. • The body supply comes mainly from the digestion of starch. • It is also know as blood sugar or dextrose. • Glucose is one of the two sugars in every disaccharide and the unit from which the polysaccharides are made almost exclusively.

10. Fructose • Fructose is the sweetest of the sugars. • Has the same chemical formula of glucose but with different structure. • Fructose occurs naturally in fruits and honey. • The amount of fructose in fruits depends on the degree of ripeness. • As the fruit ripens, some of the stored starch turns to sugars. • It is also called fruit sugar.

11. Galactose • Galactose occurs naturally as a single sugar in only few foods. • Galactose has the same number and kinds of atoms as glucose and fructose in yet another arrangement. • Galactose also is not usually found as such in the diet. But rather as a part of disaccharide ”lactose=glucose+galactose” • Milk is the primary food source of galactose. Comes mainly from digestion of milk sugars (lactose).

12. Disaccharides • Disaccharides: pairs of monosaccharides linked together. • Glucose occurs in all three, and the second member of the pair is either fructose, galactose, or another glucose. • The CHO and all other energy nutrients are put together by a reaction called condensation(links two monosaccharaides together and gives out water). and are taken apart by reaction called hydrolysis (is to break a disaccharide into two, and a molecule of water splits to provide the H & OH needed to complete the resulting monosaccharide). The hydrolysis often occurs during digestion.

13. Sucrose • Sucrose=glucose + fructose • Occurs naturally in fruits ,vegetables and grains. • To make a table sugar, sucrose is refined from the juices of sugarance and sugar beets, then granulated. • Is common table sugar, and from sugar cane, sugar beets. • Depending to the extent to which it is refined ,the product becomes the familiar brown, white, and powdered sugars available in the grocery stores. • Sucrose is readily hydrolyzed by acids and by enzyme sucrase in the small intestine into glucose and fructose.

14. Lactose • Lactose= glucose+ galactose • The principle CHO of milk . Known as milk sugar. • The sugars derived primarily from plants, except for lactose and its components galactose, which come from milk and milk products. • Lactose is the only common sugar not found in plants. • It is less soluble and less sweet than sucrose. • Remains in the intestine longer than other sugar encourage the growth of certain useful bacteria. • It is readily hydrolyses by enzyme lactase into glucose and galactose.

15. Maltose • Maltose= glucose + glucose • The two single sugar units that composed maltose are both glucose. • It is not usually found as such in the diet. • Maltose is produce whenever starch is break down-it is derived in the body from the intermediate digestive breakdown of starch. occurs during the fermentation process that yields alcohol.  only a minor constituent of few food, most notably barely.

16. polysaccharides • Composed of many single sugar units linked together. • The important polysaccharides in nutrition includestarch, glycogenand dietary fiber.

17. Starch • Starch: is long branches and unbranched chains of hundred or thousands of glucose molecules linked together. • Is insoluble polysaccharide. • Is the most dietary carbohydrates worldwide found in grains(rice and wheat), legumes(peas and beans) and tubers (potatoes and yams). • When the plant is eaten, the body hydrolyzes the starch to glucose. • Moist and heat causes grains to swell, cell may disrupt and the starch becomes soluble. Cooking renders the starch to become soluble and more accessible to digestive enzymes. • Starch grains contains two polysaccharide derived from glucose(amylose and amylopectin).

18. Because starch are more complex than simple sugars, they breakdown more slowly and supply energy over longer period of time. • Dextrin's are degradation product of starch in which glucose chains have been broken down to smaller units by partial hydrolysis. • The human body stores glucose as glycogen But plant cells store glucose as starch.

19. Glycogen • Is found only to a limited extent in meats and not at all in plants. • The human body stores much of its glucose as glycogenand it is found in the liver and muscles. • In storage many glucose molecules linked together in highly branched chains. This arrangement permits rapid hydrolysis. • When the hormonal message arrives at the storage sites, enzymes respond by attacking glycogen simultaneously, making a surge of glucose available. • These small stores of glycogen help sustain normal blood sugar during fasting and provide immediate fuel for muscle action.

21. Dietary fiber • Dietary fibers are the structural parts of plants and thus are found in all plants derived foods-vegetables, fruits, whole grains ,and legumes. • Most dietary fibers are polysaccharides. • Fibers differ from starches in that the bonds between their monosaccharaides cannot be broken down by human digestive enzymes.(Non starch polysaccharide). • Fibers pass through the body and they contribute no monosaccharide, and therefore little or no energy. • The bacteria of the gastrointestinal tract can break some fibers down, this is important to digestion and health.

22. Dietary fibers into two groups • Soluble fiber: • Indigestible food components that dissolve in water to form a gel(viscous). • Are easily digested by bacteria in the colon(fermentable). • Commonly found in oats, barely, legumes, and citrus fruit. • They are mostly associated with protecting against heart disease and diabetes by lowering blood cholesterol and glucose level,repectively. • An example is pectin from fruit, which is used to thicken jellies.

23. Insoluble fiber: • Indigestible food components that do not dissolve in water. • Don't form gels (nonviscous),and are less readily fermented. • Found mainly in whole grains(bran),vegetables. • It promotes bowel movements and alleviate constipation.

24. Types of fibers: 1- Cellulose: cellulose is the primary constituent of plant cell wall . Occurs in all vegetables, fruits and legumes. 2- Non-cellulose polysaccharides: such as pectin, gums and mucilage. 3- Lignin: woody parts of vegetables such as carrots and the small seeds of fruits (strawberries).

25. Total Fibers can be the sum of Dietary fibers and Functional fibers . Dietary fibers (all the previous). Functional fibers : fibers usually occurs naturally in plants when these fibers have been extracted from plants or manufactured and then added to foods or used in supplements.

26. Resistant starches: • A few starches are classified as dietary fibers. known as resistant starches, these starches escape digestion and absorption in the small intestine. • Starch may resist digestion for several reasons, including the individual efficiency in digesting starches and the food physical properties. • Resistant starch is common in whole legumes, raw potatoes, and unripe banana.

27. Phytic acid • It is not classified as dietary fiber, is often found accompanying them in the same foods. • The researchers have been unable to determine whether it is dietary fiber, the phytic acid or both, that binds with minerals, preventing their absorption. • This binding presents a risk of mineral deficiencies, but the risk is minimal when total fiber intake is reasonable and mineral intake is adequate.

28. Clinical importance of fibers: 1-Constipation 2-Colon cancer 3-Obesity 4-Hypoglycemia 5-Hyperglycemia 6-Diverticulosis

29. High fiber diet: • Is the dietary fibers exceed 40 gm/day. • Food sources: fruits, vegetables, bread & cereals. • Disadvantage of increasing fiber in the diet are: 1-Abdominal fullness 2-Increasing flatulence 3-Nausea and vomiting. 4-Gases 5-May interfere with mineral absorption. 6-More seriously can obstruct the GI tract.

30. Carbohydrate sources Table (1): Carbohydrate sources

32. Recommended intakes of carbohydrates • Dietary recommendations suggest that, CHO provide more than half (55 to 60 %) of energy requirement. • 5-9 servings daily of combinations of fruits and vegetables. • 6-11 servings daily of combination of breads, cereals and legumes. • The FDA (The Food and Drug Administration) set a daily value on food for fibers at 25 gram fiber daily. • The American Dietetic Association suggests that 20 - 25 grams of dietary fibers daily. • A high fiber diet is more than 40 gm/day.

34. Carbohydrates-2 Lect-3 Sara AL-Mosharruf

35. objectives • Introduction • Carbohydrates classification • Carbohydrate sources lect-2 • Recommended intakes of carbohydrates • Function of carbohydrate • Digestion , absorption and lect-3 metabolism of carbohydrate • Glucose in the body

36. Functions of carbohydrates 1- Basic fuel supply • The main function of carbohydrate is to provide the primary fuel. • Carbohydrates burn in the body at a rate of 4 kcal/gm. • Carbohydrates furnish readily available energy that needed not only for physical activities but also for all the work of the body cells.

37. 2- Reserve fuel supply • The human body reserves carbohydrate as glycogen (in liver an muscles).   • Maintain a normal blood glucose level and to prevent a breakdown of fat and protein in tissue. • People must eat carbohydrate foods regularly and fairly frequent intervals to meet energy demand.

38. 3- Special tissue functions • Liver: • glycogen reserves in the liver and muscle provide constant exchange with the body's overall energy balance system. • Reserves glycogen especially in the liver protect cell from depressed metabolic function and resulting injury.

39. Protein: in case of insufficient carbohydrate, the human body use the protein as a fuel supply which prevent protein to be used for its major role in tissue growth and maintenance. • Fat: • Insufficient carbohydrate for energy, rapid breakdown of fat would produce excess materials called ketones, which result from incomplete fat oxidation in the cell. • These ketones are acids, and can become serious.

40. 4- Central nervous system • The brain has no stored supply of glucose, therefore, it is dependent on a minute-to-minute supply of glucose from the blood. • Sustained and profound shock from blood sugar may cause brain damage.

41. 5- Fibers A. Cellulose • Celluloseit remains undigested in the gastrointestinal tract. • And provide important bulk to the diet. • This bulk helps 1 move the food mass along. 2 stimulate normal muscle action in the intestine. 3and forms the feces for elimination of waste products.

42. B. Noncellulosepolysaccharides • Absorb water and swell to large bulk. • Slow the emptying of the food from the stomach . • Bind bile acids including cholesterol in the intestine. • Prevent spastic colon pressure by providing bulk for normal muscle action. • Provide fermentation material for colon bacteria to work on.

43. Table (2): Shown that, summary of dietary fiber classes

45. Digestion , absorption and metabolism of carbohydrate • The goal is to break sugar and starches into small molecules-chiefly glucose-that the body can absorb and use. • A large starch molecule require extensive breakdown. The disaccharide needs only to be broken once. And the monosaccharide not at all. • The initial splitting begins in the mouth, and the final splitting and absorption occur in small intestine, and the conversion to common energy (glucose) takes place in the liver.

46. Carbohydrate digestion In the mouth: Mastication: the process by which food is crushed and ground by teeth .The chewing of high-fiber food slows eating and stimulate the flow of saliva. Starch: salivary glands secretes saliva into the mouth to moisten the food. The salivary enzyme amylase begins digestion. Starch Amylase small polyshcarrides, maltose(disacharride) Fibers: the mechanical action of the mouth crushes and tears fiber in food and mixes it with saliva to moisten it for swallowing.

47. In the stomach: Peristalsis: wave like muscular contraction. The swallowed bolus(a portion of food swallowed at one time) mixes with stomach acids and protein digesting enzymes, which inactivate salivary amylase. Starch: stomach acid inactivates salivary enzymes, halting starch digestion. To small extent ,the stomach acid continue breaking the starch, but it juices contain no enzymes to digest CHO. Fibers: is not digested in stomach and delays gastric emptying thereby provide feeling of fullness and satiety.

48. In the small intestine : In it most of the work of CHO digestion . Starch: the pancreas produces an amylase that is released through pancreatic duct into the small intestine. The major CHO-digesting enzyme is the pancreatic amylase which will continue breaking polysaccharides. Starch pancreatic amylase small polysaccharides, maltoses the pancreatic amylase in the duodenum breaks down all small polysaccharides into disaccharides.

49. The final step takes place in the outer membrane of the intestinal cells. The disaccharide digestion begins at this point. There specific enzymes secreted from the intestinal glands breaks down specific disaccharides. The disaccharide enzymes on the surface of the small intestinal cells hydrolyze the disaccharides into monosaccharaides Maltose maltase Glucose +Glucose Sucrose sucraseFructose+Glucose Lactose lactaseGalactose+Glucose ==>intestinal cells absorb these monosaccharaides. Fibers: is not digested ,and delays the absorption of other nutrients.

50. Large intestine: • Within 1-4 hours after a meal, all of the sugars and most of the starches have been digested. • Only fibers remain in the digestive tract. • Fibers in large I. attracts water, which softens the stool for passage without straining. • Also, bacteria in the GI tract ferment some fibers. • Most fiber passes intact through digestive tract to the large intestine. Here, bacterial enzyme digest fiber. Some fibers Bacterial Enzymes short-chain fatty acids, gas & water • Colon uses these small fat molecules for energy. Metabolism of short chain fatty acids occurs in the cells of liver. fiber therefore can contribute some energy. Depending on the extent to which they are broken down by bacteria an d the fatty acids are absorbed. • Fiber holds water ,regulate bowel activity, and bind substances such as bile ,cholesterol, and some minerals, carrying them out of the body.