Isoprenoid compounds having 27-29 carbon atoms are called steroids. Steroids with hydroxyl groups are called sterols. Animal sterols are called zoosterols and plant sterols are called phytosterols. Cholesterol is an important sterol present in the animal body. Important sterols present in plant body are Argosterol (Neurospora and Yeast), Stigasterol (Grape, Coconut and Soybean), Beta Citesterol (Grains), Spinesterol (Spinach and Cabbage), Cholesterol (Potato and Sweet Potato), Digitalin, Zymosterol, Mycosterol etc. Dr. Siddiq Publications
Biological importance of steroids
(i) Steroids act as cell signaling molecules.
(ii) It forms the cell membrane.
(iii) Cholesterol reduces the fluidity of the cell membrane.
(iv) It is a concentrated energy reservoir in the cell. But it does not provide any energy to the body.
(v) Malignant prostate cancer increases when steroid secretion is high.
(vi) Steroids act as sex hormones. Cortisol plays a role in sexual development.
(vii) Cortisol steroid digests carbohydrates and proteins and maintains water and salt balance.
(viii) Used as steroid medicine. Digitalis is used in the treatment of heart disease.
(ix) Argosterol is converted into vitamin-D by exposure to ultra-violet rays.