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Understanding Carbohydrates: Structure, Function, and Digestion

Carbohydrates are essential energy-yielding nutrients, with a caloric value of 4 Cal/g. They encompass monosaccharides, disaccharides, and polysaccharides, each playing vital roles in energy production and metabolism. Monosaccharides like glucose and fructose are isomers, while disaccharides such as sucrose and lactose form through dehydration synthesis. The digestive process involves enzymes like salivary amylase and pancreatic amylase, breaking down carbohydrates for absorption. Dietary fiber, classified as soluble and insoluble, promotes health by reducing cholesterol and supporting bowel movements.

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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 L of water 1 degree Celsius

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

  4. Glucose and Fructose

  5. Galactose

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

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

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

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

  10. Polysaccharides

  11. Starches: Grains

  12. Starches: Legumes

  13. Starches: Tubers

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

  15. 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

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

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

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

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

  20. Chemical Digestion Of CHO • Please refer to the digestive system power point and page 102 of Understanding Nutrition in order to understand carbohydrate pathway.

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

  22. 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

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

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

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

  26. Maltase • Breaks down maltose into two glucose molecules

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

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

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

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

  31. Assigned ReadingsUnderstanding Nutrition • Figure 4-10 (carbohydrate digestion) p. 104 • pp. 106-109: Blood Glucose • Table 4-2 (alternative sweeteners) pp. 116-117

  32. 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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