Assertion (A): The process of breathing is also called pulmonary ventilation. Reason (R): It involves the movement of air into and out of the lungs. MCQ with Answer and Explanation

Explanation:
Niacin is part of NAD⁺/NADH, which donates electrons to the electron transport chain to generate the proton gradient for ATP synthesis. All B vitamins contribute indirectly.

Explanation:
Iodine deficiency leads to insufficient thyroid hormone production, causing TSH hypersecretion and thyroid gland enlargement (goiter). Anemia is iron/B₁₂/folate deficiency, rickets vitamin D, scurvy vitamin C.

Explanation:
Calcitonin is produced by the parafollicular (C) cells of the thyroid gland. It lowers blood calcium levels by inhibiting osteoclast activity and promoting calcium deposition in bones. Parathyroid hormone (from parathyroid glands) raises calcium. Adrenal and pituitary glands have other functions.