The hormone that stimulates the kidney to convert 25-hydroxyvitamin D to active 1,25-dihydroxyvitamin D is:
A. ACTH
B. PTH
C. TSH
D. Calcitonin
Answer: Option B
Solution (By JKExamLibrary)
Parathyroid hormone (PTH) activates the enzyme 1-α-hydroxylase in the kidney, converting vitamin D to its active form, which then increases calcium absorption.
Consider statements about plant biology: 1. Transpiration occurs through stomata. 2. Guttaion occurs through hydathodes. 3. Phloem transports water upwards. Which are correct?
Explanation:
Transpiration is the loss of water vapor primarily through the stomata on the leaf surface. Guttation is the exudation of liquid water from the margins of leaves through specialized structures called hydathodes, usually at night when root pressure is high. Phloem is responsible for the translocation of organic food (bidirectional), while xylem transports water and minerals upwards. Thus, statements 1 and 2 are correct.
Explanation:
Lycopene is a red carotenoid pigment that accumulates in ripe tomatoes and watermelon. Beta-carotene is orange, chlorophyll green, anthocyanin purple/red in some plants.
Explanation:
Cardiac muscle cells are striated, branched, and connected by intercalated discs containing gap junctions for synchronized contraction. They are involuntary. Multinucleated syncytium is typical of skeletal muscle. Spindle-shaped non-striated cells characterize smooth muscle. Voluntary control is for skeletal muscle. Intercalated discs allow rapid ion passage, enabling the heart to function as a syncytium.
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