Steroids are a group of lipids that contain a cyclic ring structure called cyclopentanoperhydrophenanthrene. The phenanthrene nucleus consist of three 6-membered carbon rings (A, B, C) and one 5-membered carbon ring(D) fully saturated with hydrogen.
Steroids include:
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Cholesterol which is found in the cell membrane of organisms and in the blood.
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Steroid hormones- Sex hormones like Testosterone, Estrogens.
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Adrenal cortex hormones
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Bile acids
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Vitamin D