Which of the Following Endocrine Glands Contributes to Setting the Body's Biological Clock?

Correct Answer: B

Rationale: The correct answer is B: Pineal gland. The pineal gland secretes melatonin, a hormone that regulates the body's sleep-wake cycle, thus contributing to setting the body's biological clock. This gland responds to light and darkness, helping to synchronize our internal clock with the day-night cycle. The pituitary gland (A) regulates various hormones but not specifically the biological clock. The thymus gland (C) is responsible for immune function, not the biological clock. The adrenal gland (D) secretes hormones related to stress response, not the biological clock. In summary, the pineal gland is key in regulating the body's biological clock through melatonin secretion, making it the correct choice.

Correct Answer: C

Rationale: Rationale for Correct Answer C: Oligosaccharidase deficiency leads to osmotic diarrhea because the incomplete breakdown of oligosaccharides in the small intestine results in unabsorbed sugars attracting water, causing diarrhea. This is a direct consequence of the deficiency in enzymes responsible for breaking down oligosaccharides. This is why Choice C is correct. Summary of Incorrect Choices: A: Salivary amylase works best at a neutral pH of around 6.7, not alkaline pH. B: Lactose intolerance is due to a deficiency in lactase enzyme, not related to carbohydrate digestion in the small intestine. D: Salivary amylase is inactivated in the acidic environment of the stomach, so it does not continue to digest carbohydrates there.

Correct Answer: D

Rationale: The correct answer is D: amylase. Gastric juice primarily consists of hydrochloric acid, pepsin, and mucus. Amylase is an enzyme produced in the pancreas, not in the stomach. It functions in the small intestine to break down carbohydrates. Therefore, amylase is not a normal component of gastric juice. Choices A, B, and C are incorrect because HPO42- (phosphate ions), mucus, and lipase are all typically found in gastric juice.

Correct Answer: A

Rationale: The correct answer is A: cAMP. cAMP, or cyclic adenosine monophosphate, does not release large amounts of energy on breakdown compared to the other choices. Here's the rationale: 1. ATP (Choice B) is known as the energy currency of the cell and releases a significant amount of energy when broken down. 2. Creatine phosphate (Choice C) is a high-energy compound that can rapidly donate its phosphate group to regenerate ATP. 3. ADP (Choice D) releases energy when converted to ATP through phosphorylation. 4. cAMP (Choice A) is a secondary messenger involved in signal transduction and does not store or release energy like ATP or creatine phosphate.

Correct Answer: B

Rationale: The correct answer is B because men lose about 0.6mg of iron per day through various physiological processes like shedding skin cells and hair. This loss must be replenished through dietary intake to maintain iron balance. Choice A is incorrect as iron is more readily absorbed in the ferrous form. Choice C is incorrect as the average daily iron intake is around 18mg. Choice D is incorrect ascorbic acid enhances iron absorption rather than reducing it.