Vitamins are organic compounds that are required by advanced animals in small amounts on a regular basis. Like essential amino acids, there are 13 vitamins that are required but not produced by the human system. Unlike essential amino acids, these vitamins are required in minute quantities. If deficient or in excess, certain maladies occur in humans, such as beriberi, anemia, rickets, and skin lesions. In general, vitamins are coenzymes, or parts of enzymes, that function to assist a specific enzyme to catalyze (increase the rate of) a reaction. Some vitamins are fat soluble and others are water soluble.
Fat-soluble vitamins are probably the most common vitamins for some people. Unlike water-soluble vitamins, they remain stored in the fat deposits of a body for long periods of time and may accumulate to overdose levels. Note that the only vitamin humans can make is Vitamin D. Vitamin D is made when cholesterol is acted upon by enzymes and sunlight. It should also be noted that the fat-soluble Vitamin K is produced in small quantities in the human intestine by the action of mutually beneficial intestinal bacteria.
Water-soluble vitamins generally function within the cell to help catalyze cellular reactions such as cellular respiration. For your reference, cellular respiration is the process of harvesting energy from the breakdown of food molecules that takes place inside individual cells. Unlike fat-soluble vitamins, excess water-soluble vitamins do not remain stored in the body, but are excreted in urine and feces. Water-soluble vitamins include the eight different types of B complex vitamins and Vitamin C.
Minerals are naturally occurring inorganic substances required in trace amounts for normal body functions such as the development of strong bones and teeth, proper muscle and nerve functions, and construction of red blood cells. Like vitamins, these essential minerals are not produced by humans, so they must be consumed on a regular basis. Because they are water soluble, excessive amounts are eliminated through normal urinary functions and perspiration.
Excerpted from The Complete Idiot's Guide to Biology © 2004 by Glen E. Moulton, Ed.D.. All rights reserved including the right of reproduction in whole or in part in any form. Used by arrangement with Alpha Books, a member of Penguin Group (USA) Inc.