Which is TRUE in respect to insulin secretion?

Correct Answer: A

Rationale: Insulin secretion depends on glucose entry into β cells via GLUT2, triggering Ca2+ influx (not efflux of K^+). Metformin enhances sensitivity, not secretion, and cAMP promotes it.

Correct Answer: D

Rationale: Fat stores vastly exceed carbohydrate (glycogen) stores, approximately 40:1 in a typical human, reflecting fat's higher energy density.

Correct Answer: C

Rationale: Ketone bodies form during glucose deficiency (e.g., fasting), are acids, but are metabolized by extrahepatic tissues, not easily in the liver.

Correct Answer: B

Rationale: VIP (vasoactive intestinal peptide) relaxes smooth muscle and increases intestinal water/electrolyte secretion.

Correct Answer: D

Rationale: Parathormone, or parathyroid hormone, is produced and secreted by the parathyroid glands. Low calcium levels will stimulate release of parathyroid hormone, which increases the plasma level of calcium. Parathormone acts on the renal tubules to increase the excretion of phosphorus in the urine and to stimulate the reabsorption of calcium. Parathormone also acts on bone, causing the release of calcium from the bone into the bloodstream.