Which of the following is the primary target organ for the hormone insulin?
A. Brain
B. Heart
C. Kidney
D. Liver
Answer: Option D
Solution (By JKSSB Mock Tests)
Insulin acts primarily on liver, muscle, and adipose tissue. The liver is a key target where insulin promotes glycogenesis (glucose to glycogen), glycolysis, and lipogenesis, and inhibits gluconeogenesis, lowering blood glucose. Muscle and adipose tissue also respond. Brain takes up glucose independently of insulin via GLUT1 transporters. Thus liver is a principal target.
Explanation:
Frederick Griffith in 1928 demonstrated transformation by showing that heat-killed virulent pneumococci could transfer virulence to live non-virulent bacteria. Avery et al. later identified the transforming principle as DNA.
Explanation:
Beriberi results from lack of thiamine (B₁), affecting the nervous and cardiovascular systems. It manifests as dry beriberi (peripheral neuropathy) or wet beriberi (heart failure). Pellagra is niacin deficiency, scurvy vitamin C, rickets vitamin D. Thiamine is a coenzyme in carbohydrate metabolism.
Explanation:
The Krebs cycle (citric acid cycle) occurs in the mitochondrial matrix in eukaryotes. The enzymes for the cycle are soluble in the matrix. The inner membrane houses the electron transport chain and ATP synthase. Cytoplasm is the site of glycolysis, chloroplast stroma is the site of the Calvin cycle. Thus, the matrix is the correct location.
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