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Understanding Carbohydrates: Structure, Function, and Digestion

Carbohydrates are energy-yielding nutrients that provide 4 cal/gr. This overview covers their types—monosaccharides (e.g., glucose, fructose), disaccharides (e.g., sucrose, lactose), and polysaccharides (e.g., starch, glycogen). It distinguishes between anabolic and catabolic reactions, with a focus on digestion through enzymes like salivary amylase and pancreatic amylase. The importance of dietary fiber and its categories—soluble and insoluble—is highlighted. Essential for energy, blood glucose maintenance, and digestive health, understanding carbohydrates is crucial for nutrition.

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Understanding Carbohydrates: Structure, Function, and Digestion

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  1. CARBOHYDRATES

  2. Energy Yielding Nutrient • All CHO have a caloric value of 4 cal/gr • Reminder: calorie- measurement of energy • Heat energy needed to raise 1 gr of water 1 degree C

  3. Saccaharides • Monosaccharides: C6H12O6 • The monosaccharides are isomers • Fructose • Galactose • Glucose

  4. Glucose and Fructose

  5. Isomers • Def: compounds that have the same chemical formula • Champ and Harvey, Biochemistry. Lippincott. 2nd edition

  6. Dissacharides • Created with the Dehyration Synthesis of Monosaccharides • Anabolic Chemical Reaction • C6H12O6 + C6H12O6 = C12H22O11 + H20 • Hydrolysis is a Catabolic Chemical Reaction

  7. Inquiry Exercise • Differentiate between catabolic and anabolic chemical reactions. • Differentiate between dehydration synthesis and hydrolysis

  8. The Dissacharides • Sucrose(cane sugars) = glc + frc • Lactose(dairy sugars) = glc + gal • Maltose(seed sugars) = glc + glc

  9. Polysaccharides

  10. Starches: Grains

  11. Starches: Legumes

  12. Starches: Tubers

  13. Inquiry Exercise • List six types of grains • List five types of legumes • List three types of tubers

  14. GLYCOGEN • The structural analogue to starches • It is a glucose polymer found in muscle, the liver, stomach and brain • It is synthesized by the liver when we are in a “fed” state • It is released by liver when blood glucose levels drop….”fast” state

  15. Fiber • Fiber is a non-digestible polysacharide. It does not have caloric value • There are two categories: • Soluble • Insoluble

  16. Soluble Fiber • Easily dissolve in water • They are considered heart healthy because they lower blood cholesterol levels • Pectin is an example of soluble fiber

  17. Insoluble fiber • Do not dissolve in water • Promote colon health by promoting bowel movements, lessening constipation and reducing diverticulosis

  18. Dietary Intake • Recommended dietary fiber intake is 25-35g per day

  19. Chemical Digestion Of CHO • Please refer to the digestive system power point in order to understand carbohydrate pathway.

  20. CHO Enzymes • Salivary Amylase: component of saliva • It functions to begin the digestion of polysaccharides • Neutralized by stomach acid

  21. Pancreatic Amylase • Secreted by the exocrine (acini) cells of the pancreas • It enters the duodenum via the pancreatic and common bile ducts • It breaks down polysaccharides into the disaccharides

  22. Duodenal Enzymes • There are three duodenal enzymes: • Sucrase • Lactase • Maltase

  23. Sucrase • Sucrase breaks down sucrose into glucose and fructose • Is this an anabolic or catabolic chemical reaction?

  24. Lactase • Lactase breaks lactose into glucose and galactose. • Lack of lactase production indicates what digestive disorder? What are the symptoms?

  25. Maltase • Breaks down maltose into to glucose molecules

  26. Absorption • All of the monosaccharides are absorbed and transported to the liver. • All monosaccharides can be converted into glucose by the liver because?

  27. Liver • The liver will • Convert monosaccharides into glucose to be part of blood glucose • Create glycogen: glycogenesis • Create lipids: lipogenesis(remember the carbohydrate hypothesis?)

  28. Function(s) of CHO • Energy • Blood glucose • Glycogen

  29. Function(s) of Fiber • Decrease blood cholesterol • Increase bowel movements

  30. Assigned Readings • Figure 4-10 (carbohydrate digestion) p. 104 • pp. 107-111: Blood Glucose • Table 4-2 (alternative sweeteners) pp. 116-117

  31. Acknowledgements • Unless otherwise noted, all information, images and assignments are adapted or taken from • Whitney and Rolfes (2011). Understanding Nutrition. 12 edition. Wadsworth Cengage Learning.

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