DR MARK J. WINTER / SCIENCE PHOTO LIBRARY DR MARK J. WINTER / SCIENCE PHOTO LIBRARY
Vitamin A. Molecular model of the retinoic acid form of vitamin A. Retinoic acid is one of three forms of vitamin A; the other two are retinol and retinal. The chemical formula for retinoic acid is C20.H28.O2. Atoms are represented as spheres and are colour-coded: carbon (blue), hydrogen (gold) and oxygen (red). Vitamin A plays an important role in maintaining healthy skin and mucous membranes, as well as in growth, reproduction and night vision. It can be made in the body from the precursor beta carotene found in vegetables and fruit. It is also found in liver and dairy products. Deficiencies in vitamin A can lead to slow growth and night blindness. Excessive doses can be toxic, causing aches and pains and in some extreme cases liver failure and death.
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