Which is TRUE, Insulin:

Correct Answer: C

Rationale: Insulin promotes ketone uptake by muscles during glucose abundance, not ketogenesis (a glucagon effect). It increases amino acid uptake and protein synthesis, not catabolism.

Correct Answer: D

Rationale: PTH binds to membrane G-protein-coupled receptors, while cortisol, aldosterone, 1,25-DHCC, and thyroxine act via intracellular nuclear receptors.

Correct Answer: B

Rationale: Folate is absorbed via a proton-coupled transporter, not Na^+-dependent like thiamine, niacin, riboflavin, and pyridoxine.

Correct Answer: C

Rationale: VIP, GIP, and glucagon do not stimulate gastrin; atropine doesn't inhibit it, amino acids do stimulate, secretin inhibits, and epinephrine can increase it.

Correct Answer: A

Rationale: The esophagus lacks BER, relying on peristalsis triggered by swallowing, unlike other GIT segments.