The vitamin that is also a hormone, synthesized by the skin upon exposure to sunlight, is:
A. Vitamin D
B. Vitamin C
C. Vitamin A
D. Vitamin B₁
Answer: Option A
Solution (By JKSSB Mock Tests)
Vitamin D (cholecalciferol) is unique as it can be synthesized in the skin from 7-dehydrocholesterol in the presence of UV-B radiation. It acts as a hormone to regulate calcium and phosphate homeostasis. It must be activated in the liver and kidneys. It is also obtained from dietary sources like fatty fish, egg yolk. Deficiency causes rickets/osteomalacia.
Consider statements about human diseases: 1. Influenza is caused by a virus. 2. Leprosy is caused by a fungus. 3. Malaria is transmitted by Anopheles mosquito. Which are correct?
Explanation:
Influenza (flu) is a respiratory illness caused by the influenza virus. Malaria is a parasitic disease caused by Plasmodium and transmitted exclusively by the bite of an infected female Anopheles mosquito. Leprosy (Hansen's disease) is a chronic infectious disease caused by the bacterium Mycobacterium leprae, not a fungus. Thus, statements 1 and 3 are correct.
Explanation:
Renin is secreted by juxtaglomerular cells of the kidney in response to low blood pressure or sodium. It converts angiotensinogen to angiotensin I, initiating the RAAS. Liver produces angiotensinogen, adrenal aldosterone, heart ANP.
Explanation:
Adenylyl cyclase converts ATP to cyclic AMP, a second messenger. Guanylyl cyclase makes cGMP, phospholipase C produces IP₃/DAG, PKA is activated by cAMP.
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