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Veterinary Biochemistry- ICAR JRF/SRF 2024
MCQ (Single Correct)
Active form of vitamin D is released from
- Stepwise Biosynthesis of Active Vitamin D:
- Skin: 7-dehydrocholesterol is converted by solar UV light into cholecalciferol (Vitamin $D_3$).
- Liver: Cholecalciferol undergoes 25-hydroxylation by hepatic 25-hydroxylase to form 25-hydroxyvitamin $D_3$ [calcidiol, $25(OH)D_3$].
- Kidney: Calcidiol is transported to the proximal convoluted tubules of the Kidney, where the mitochondrial enzyme $1\alpha$-hydroxylase (stimulated by parathyroid hormone) adds a second hydroxyl group to produce 1,25-dihydroxyvitamin $D_3$ [Calcitriol, $1,25(OH)_2D_3$].
- Calcitriol is the biologically active hormonal form released by the kidney into the systemic circulation to regulate calcium and phosphate homeostasis.
- nalysis:
- (Kidney): Correct organ releasing active calcitriol.
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