Derivatives of water-soluble vitamins serve as coenzymes in the metabolism of carbohydrates, lipids, and proteins. Thiamine, for example, is needed for the activity of the enzyme that converts pyruvic acid to acetyl coenzyme A. Riboflavin and niacin are needed for the production of FAD and NAD, respectively. FAD and NAD serve as coenzymes that transfer hydrogens dur ing cell respiration (chapter 4; see fig. 4.17). Pyridoxine is a co-factor for the enzymes involved in amino acid metabolism. Deficiencies of the water-soluble vitamins can thus have widespread effects in the body (table 19.3).
Free radicals are highly reactive molecules that carry an unpaired electron. Such free radicals can damage tissues by removing an electron from, and thus oxidizing, other molecules. Vitamin C (a water-soluble vitamin) and vitamin E (a fat-soluble vitamin) function as antioxidants through their ability to inactivate free radicals. These vitamins may afford protection against some of the diseases that may be caused by free radicals.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.