With regard to carbohydrate digestion:

Correct Answer: C

Rationale: Step-by-step rationale for choice C being correct: 1. Oligosaccharidase deficiency impairs breakdown of oligosaccharides in the small intestine. 2. Undigested oligosaccharides draw water into the intestines, causing osmotic diarrhea. 3. This leads to increased fluid content in the stool, resulting in osmotic diarrhea. 4. This process does not involve salivary amylase or lactose intolerance.

Correct Answer: C

Rationale: The correct answer is C: GIP. GIP, or glucose-dependent insulinotropic peptide, is the most important hormone in insulin secretion. It is released by the intestines in response to glucose intake, stimulating the release of insulin from the pancreas. Gastrin (A) is involved in gastric acid secretion, not insulin. CCK (B) and secretin (D) are involved in digestion and pancreatic enzyme secretion, not insulin regulation. So, GIP is the correct answer as it directly stimulates insulin release in response to glucose levels.

Correct Answer: D

Rationale: The correct answer is D. Thyroxine is deiodinated in the liver to T3, so approximately 33% of thyroxine is converted to the more active form, triiodothyronine. This conversion is important for regulating metabolic processes in the body. Choices A and C are incorrect because thyroxine is primarily bound to thyroxine-binding globulin in the plasma, not albumin, and it does not stimulate TSH release. Choice B is incorrect because T3 is actually more potent than thyroxine, not the other way around.

Correct Answer: B

Rationale: Rationale for correct answer (B - leucine): Leucine is an essential amino acid, meaning it cannot be synthesized by the body and must be obtained through diet. It plays a crucial role in protein synthesis, muscle repair, and growth. It is essential for overall health and well-being. Summary of why other choices are incorrect: A - taurine: Taurine is a conditionally essential amino acid, not nutritionally essential. C - glutamate: Glutamate is a non-essential amino acid, as the body can synthesize it. D - alanine: Alanine is a non-essential amino acid, as the body can also produce it.

Correct Answer: B

Rationale: The correct answer is B: goiter. An enlargement of the thyroid gland is specifically referred to as a goiter. This condition can be caused by iodine deficiency or other factors affecting thyroid hormone production. Acromegaly (A) is a disorder caused by excessive growth hormone, unrelated to the thyroid. Parathyroidism (C) refers to issues with the parathyroid glands, not the thyroid. Cushing's disease (D) is a condition involving excessive cortisol production, not thyroid enlargement. Therefore, the correct term for an enlarged thyroid gland is goiter.