... >> Natural Science >> Zoology >> Vitamin
Highest Rated Sign
Nobody has posted a sign yet.
Definition: An organic substance required in small amounts for normal metabolic function; must be supplied in the diet or by intestinal flora because the organism cannot synthesize it. An exception is vitamin D3, which is manufactured in the skin in the presence of sunlight.
Source: Hickman, C.P., et al. 2011. Integrated Principles of Zoology. Fifteenth Edition. McGraw-Hill Higher Education.