Vitamins fall into the category of micronutrients, meaning that they're compounds that humans require in small amounts. They don't provide energy, but do engage in chemical reactions and have activity in the body. The structures of vitamins determine their ability to participate in chemical reactions, and vary considerably by vitamin type.
Significance
In biochemistry, the shapes or structures of molecules are important to function and activity in the body. Molecules, including vitamins, react with other molecules and bind to receptors on cells based upon their shapes. As such, vitamin structures provide information about the activity of the vitamin in the body, and in some cases, provide information about how the vitamin is derived or synthesized in the body from its precursor chemicals.
Function
In many cases, vitamin structure provides information about function. Both vitamins C and E are antioxidants, and as such, they have chemical structures that are easily oxidizable, meaning that it's possible for the vitamins to lose electrons from their structures. According to doctors Reginald Garrett and Charles Grisham in their book "Biochemistry," this is important, because certain toxins steal electrons from molecules in the body, and if DNA and other cellular molecules lose electrons, this can damage the cell. Vitamins C and E sacrifice electrons to maintain cellular integrity.
Features
Specific features of vitamin structures sometimes play a role in--and give information about--the reactions in which the vitamin participates. Vitamin A, for instance, is important to sensing light in the retina of the eye. The vitamin structure contains a carbon-carbon double bond that isomerizes, meaning changes orientation, in the presence of light, which sends the chemical signal that there's light entering the eye. According to Garrett and Grisham, only a carbon-carbon double bond would be able to respond to light in this way.
Considerations
Some vitamins have structures similar to the compounds from which they are derived. Doctors Mary Campbell and Shawn Farrell write in their book "Biochemistry" that the body makes vitamin D from cholesterol in the presence of sunlight, though the vitamin can also be obtained from food. The structure of vitamin D is similar to that of cholesterol, making the vitamin's biological origin quite clear. Because of its similarity to fat-based cholesterol, vitamin D is a fat-soluble vitamin.
Expert Insight
Vitamins, because they're organic molecules--meaning that they are molecules found in living organisms--are made primarily of carbon and hydrogen. Other common elements in vitamins include oxygen, and a few vitamins also contain nitrogen--particularly the B vitamins. These four elements make up the vast majority of all organic molecules, including both the structural and functional molecules of the body, as well as nutritional molecules, according to Campbell and Farrell.
References
- "Biochemistry"; Reginald Garrett, Ph.D. and Charles Grisham, Ph.D.; 2007
- "Biochemistry"; Mary Campbell, Ph.D. and Shawn Farrell, Ph.D.; 2005
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