- 7-Dehydrocholestrol (provitamin D3): In the skin, UV rays of the sun convert 7-dehydrocholesterol to cholecalciferol. Hence, 7-dehydrocholesterol is called as provitamin D3. This concept explains the use of sunshine in preventing rickets, a disease caused by vitamin D deficiency.
- Ergosterol (provitamin D2): When irradiated by UV rays, ergosterol is converted to vitamin D2 by the opening of ring B of the sterol. Hence, ergosterol is also called as provitamin D2.
- Sitosterol: Sitosterol decreases the intestinal absorption of exogenous and endogenous cholesterol; this lowers the blood cholesterol level.
- Biomedical importance of gangliosides: Gangliosides are named components of membranes. The sugar units and sialic acid section of the molecule are ‘water soluble (hydrophilic) and negatively charged, whereas the ceramide portion is lipid soluble (hydrophobic). The gangliosides, therefore, can serve as specific membranes’ binding sites.
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