Which of the following is NOT true of testosterone?

Correct Answer: D

Rationale: The correct answer is D because testosterone is not controlled by the thyroid gland. Testosterone is primarily produced in the testes and regulated by the hypothalamus and pituitary gland. The other choices (A, B, C) are all true of testosterone. Testosterone is responsible for the growth of the penis and testes (A), development of male secondary sex characteristics (B), and can potentially lead to baldness due to its effects on hair follicles (C). Thyroid gland primarily regulates metabolism and energy levels, not testosterone production.

Correct Answer: C

Rationale: The correct answer is C: Pancreas. The pancreas is the endocrine gland responsible for producing insulin, which regulates blood sugar levels. It is located behind the stomach and plays a crucial role in maintaining glucose balance in the body. The other choices, A: Adrenal, B: Parathyroid, and D: Liver, do not normally produce insulin. Adrenal glands produce hormones like adrenaline and cortisol, the parathyroid regulates calcium levels, and the liver performs various metabolic functions but does not produce insulin. Therefore, the pancreas is the correct choice for insulin production.

Correct Answer: D

Rationale: The correct answer is D: folate. Folate absorption is not Na+ dependent as it is primarily absorbed in the small intestine through a carrier-mediated process that is independent of sodium. Thiamin, riboflavin, and niacin absorption, on the other hand, are Na+ dependent processes that rely on sodium co-transporters for uptake in the small intestine. Thiamin is absorbed through a sodium-dependent active transport system, riboflavin requires a sodium-dependent carrier protein for absorption, and niacin absorption involves a sodium-dependent transporter in the small intestine. Therefore, folate is the only option that is not Na+ dependent for absorption.

Correct Answer: D

Rationale: The correct answer is D: stomach. Proteins are broken down into amino acids through the process of digestion. In the stomach, proteins are broken down into smaller peptides, not free amino acids. The final step of liberating proteins into free amino acids occurs in the enterocyte cytoplasm, where absorbed nutrients are further processed. The brush border of the small intestine is where the final stages of digestion take place before absorption. The small intestine lumen is the space where digestion occurs, but the actual liberation of proteins into free amino acids happens in the enterocyte cytoplasm.

Correct Answer: D

Rationale: The correct answer is D: acetylcholine. Parietal cells in the stomach are primarily stimulated by acetylcholine to secrete hydrochloric acid. Acetylcholine binds to muscarinic receptors on parietal cells, leading to an increase in intracellular calcium levels and subsequent acid secretion. Prostaglandins (choice A) actually inhibit acid secretion, making it an incorrect choice. Aspirin (choice B) is known to damage the gastric mucosa and does not directly stimulate parietal cells. Vinegar (choice C) is acidic but does not specifically target parietal cells for acid secretion. Therefore, the correct choice is acetylcholine as it directly stimulates parietal cell secretion through muscarinic receptors.