CARBOHYDRATES

1. CARBOHYDRATES

2. The term “carbohydrate” refers to a group of molecules composed of carbon, hydrogen, and oxygen. There are two groups: Simple carbohydrates (also called “sugars”) Complex carbohydrates

3. The term “carbohydrate” refers to a group of molecules composed of carbon, hydrogen, and oxygen. • There are two groups: • Simple carbohydrates (also called “sugars”) • Complex carbohydrates • In fact, they are related: • The complex carbohydrates are formed by • linking together many simple carbohyrates • and • The simple carbohydrates can be formed by • breaking apart the complex carbohydrates • We get carbohydrates in our diets from eating • plants and, to smaller degree from milk and meat.

4. The simple carbohydrates are the monosaccharides and the disaccharides Simple Carbohydrates:

5. The simple carbohydrates are the monosaccharides and the disaccharides Although there are dozens of known monosaccharides and disaccharides, only a small number are important nutritionally because they are found in our food. Monosaccharides: All have formula C6H12O6 Simple Carbohydrates:

6. Glucose (also called “dextrose”) is the most abundant and most important monosaccharide. Simple Carbohydrates: Monosaccharides

7. Glucose (also called “dextrose”) is the most abundant and most important monosaccharide. All green plants produce glucose from carbon dioxide, water, and sunlight (energy) Gives food a sweet taste Glucose is the primary “fuel molecule” our cells use to produce energy so It is the sugar carried around the body in the blood Simple Carbohydrates: Monosaccharides

8. Fructose (also called “levulose” or “fruit sugar”) is also very sweet Simple Carbohydrates: Monosaccharides

9. Fructose (also called “levulose” or “fruit sugar”) is also very sweet Occurs naturally in fruits, vegetables, honey, and corn syrup. Some cells can use fructose as a fuel molecule, but most cells convert it to glucose instead Simple Carbohydrates: Monosaccharides

10. Galactose - rarely found alone in nature Usually combined with glucose Simple Carbohydrates: Monosaccharides

11. Galactose - rarely found alone in nature Usually combined with glucose Found in milk Cells convert galactose to glucose for energy May be part of cell membranes Simple Carbohydrates: Monosaccharides

12. Simple Carbohydrates: Disaccharides Disaccharides are two monosaccharides linked together

13. Simple Carbohydrates: Disaccharides Disaccharides are two monosaccharides linked together Three disaccharides are dietarily important: Sucrose Lactose Maltose All have formula C12H22O11

14. Simple Carbohydrates: Disaccharides Sucrose = glucose + fructose Found in sugarcane, sugarbeets “Table Sugar” – only sweetener that can be called “sugar” on food labels in United States

15. Simple Carbohydrates: Disaccharides Lactose = glucose + galactose “Milk Sugar”

16. Simple Carbohydrates: Disaccharides Maltose = glucose + glucose Found in partially digested starch and in germinating cereal grains

17. Complex Carbohydrates Chains of two or more monosaccharides Oligosaccharides = shorter chains Polysaccharides = longer chains

18. Complex Carbohydrates: Oligosaccharides Consist of 3-10 monosaccharides Found in legumes, milk Forms receptors on many cell membranes Not digestible by humans = fiber May be added to food: inulin oligofructose raffinose maltotriose

19. Starch: How plants store energy Found in grains, legumes, and tubers Long chains of glucose units: Amylose—straight chains Amylopectin—branched chains Complex Carbohydrates: Polysaccharides

20. Glycogen How animals (including humans) store energy Found in meat, liver Long, branching chains of glucose units: Formed in liver and muscle when blood glucose levels are high Can be broken down to provide glucose when blood glucose levels get low Complex Carbohydrates: Polysaccharides

21. Cellulose Complex Carbohydrates: Polysaccharides Indigestible chains of monosaccharides = “fiber” - speeds up gastrointestinal movement - increases fecal mass - slows breakdown of starch - slows absorption of glucose Found in all plants, “Functional” fiber: isolated and added to foods Can be use as a supplement

22. Other forms of fiber Complex Carbohydrates: Polysaccharides = Indigestible chains of monosaccharides Pectins Gums Lignans Beta glucans Chitins Found in all plants, “Functional” fiber: isolated and added to foods Can be use as a supplement

23. Complex Carbohydrates

24. Dietary fiber: Possible role in weight control Better control of blood glucose Reduced risk of heart disease Healthier gastrointestinal functioning Negative effects of excess fiber Increased water consumption Can bind small amounts of minerals Complex Carbohydrates:

25. Complex carbohydrates (amylose, amylopectin) broken down to form disaccharides and monosaccharides: Mouth: Salivary amylase begins digestion Stomach: No carbohydrate digestion Small intestine: Pancreatic amylase finishes digestion Carbohydrate Digestion:

26. Disaccharides (sucrose, maltose, lactose) broken down to form monosaccharides: Small intestine: Pancreatic enzymes Enzymes from intestinal cells (sucrase, maltase, lactase) Carbohydrate Digestion:

27. Carbohydrate Digestion: These enzymes are highly specific For example: - Amylase digests amylose but not amylopectin - Lactase digests lactose but not maltose or sucrose - Maltase digests maltose but not lactose or sucrose - Sucrase digests sucrose but not maltose or lactose Remember: Some carbohydrates can not be digested; fiber & “resistant” starch

28. Carbohydrate Absorption: Monosaccharides are absorbed from the small intestine

29. Carbohydrate Absorption: Monosaccharides are absorbed from the small intestine and carried by the blood to the liver

30. Carbohydrate Absorption: Liver: Converts other monsaccharides to glucose Stores excess glucose as glycogen Monosaccharides are absorbed from the small intestine and carried by the blood to the liver

31. Carbohydrate Absorption: Liver: Converts other monsaccharides to glucose Stores excess glucose as glycogen Liver: Breaks down glycogen to release glucose back into the blood when needed. Monosaccharides are absorbed from the small intestine and carried by the blood to the liver

32. Glucose is our primary fuel source so It is important to maintain normal blood glucose levels and It is important for glucose to get from the blood into cells Carbohydrate Metabolism:

33. Glucose is our primary fuel source so It is important to maintain normal blood glucose levels and It is important for glucose to get from the blood into cells These processes are primarily regulated by two hormones Insulin Glucagon Both are secreted by the pancreatic islets Carbohydrate Metabolism:

34. Carbohydrate Metabolism:

35. Insulin promotes: (i) Energy storage glucose glycogen (glycogenesis) (ii) Protein synthesis glucose amino acids protein (iii) Fat synthesis glucose fatty acids triglycerides(fat) Carbohydrate Metabolism:

36. Carbohydrate Metabolism: Disorders Normal Blood Glucose: 70-110 mg/100 ml of blood

37. Persistent high blood glucose levels = Hyperglycemia Insufficient insulin >125 mg/100 ml Too much glucagon Most common cause = diabetes mellitus Carbohydrate Metabolism: Disorders Normal Blood Glucose: 70-110 mg/100 ml of blood

38. Persistent high blood glucose levels = Hyperglycemia Insufficient insulin >125 mg/100 ml Too much glucagon Most common cause = diabetes mellitus Persistent low blood glucose levels = Hypoglycemia Too much insulin <50 mg/100 ml Insufficient glucagon Most common causes = insulin overdose in diabetes starvation strenuous exercise Carbohydrate Metabolism: Disorders Normal Blood Glucose: 70-110 mg/100 ml of blood

39. Diabetes Mellitus: Glucose unable to enter cells so Blood glucose levels rise (hyperglycemia) Complications: Hypertension Heart damage Kidney damage Nerve damage Blood vessel damage Eye damage Carbohydrate Metabolism: Disorders

40. Carbohydrate Metabolism: Disorders Diabetes mellitus: Type 1 or “insulin dependent” diabetes: Lack of insulin production Type 2or “insulin independent” diabetes: Cells are resistant to insulin

41. Carbohydrate Metabolism: Disorders Diabetes mellitus: Type 1 or “insulin dependent” diabetes: Lack of insulin production Type 2or “insulin independent” diabetes: Cells are resistant to insulin Usually present as “prediabetes” first Gestational diabetes: occurs during pregnancy

43. Carbohydrate Metabolism: Disorders Diabetes mellitus: Best prevention: Healthful diet Regular exercise Healthy weight Don’t smoke Monitor blood sugar if you have genetic predisposition

44. Recommended carbohydrate intake: Recommended Daily Allowance = 130 grams per day Acceptable Macronutrient Distribution Range = 45–65% of calories Carbohydrates:

45. Recommended carbohydrate intake: Recommended Daily Allowance = 130 grams per day Acceptable Macronutrient Distribution Range = 45–65% of calories Choose carbohydrates wisely: fiber-rich fruits vegetables whole grains high-fiber cereal Because: Not all carbohydrate sources have the same effect on blood glucose levels Carbohydrates:

46. Carbohydrates: Each type of food has a glycemic index which measures its effects on blood sugar levels.

47. Carbohydrates: Each type of food has a glycemic index which measures its effects on blood sugar levels. Carbohydrates that break down quickly during digestion and release glucose rapidly for absorption into the bloodstream have a high glycemic index

48. Carbohydrates: Each type of food has a glycemic index which measures its effects on blood sugar levels. Carbohydrates that break down quickly during digestion and release glucose rapidly for absorption into the bloodstream have a high glycemic index Carbohydrates that break down more slowly, releasing glucose more gradually for absorption into the bloodstream, have a low glycemic index.

49. Carbohydrates: Low glycemic index: Most vegetables, fruits, legumes, (55 or less) whole grains, nuts, milk, citrus juices, foods low in carbohydrates Moderate glycemic index: Whole wheat products, honey, (56 to 69) brown or basmati rice, bran, baked potato, sweet potato High glycemic index: White bread, white rice, breakfast (70 and above) cereals, waffles, chips, candy, table sugar (Pure glucose: glycemic index = 100)

50. Moderating sugar intake: Choose food with lower glycemic index Use less added sugar Limit soft drinks, sugary cereals, and candy Choose fresh fruits or those canned in water or juice Carbohydrates: