Correct Answer: B

Rationale: The correct answer is B: Phytochemicals. Phytochemicals in soy foods can mimic estrogen and may have health benefits. Indispensable amino acids are essential amino acids that the body cannot produce on its own. Neurotransmitters are chemical messengers in the nervous system. Metabolic by-products are substances produced during metabolism.

Correct Answer: B

Rationale: The correct answer is B: Intestinal mucosa. The intestinal mucosa has the highest rate of protein turnover due to its rapid cell renewal. The skin, muscle, and adipose tissue do not exhibit protein turnover rates as high as the intestinal mucosa. Skin cells turnover relatively slower compared to the rapid renewal of intestinal mucosa cells. Muscles have a moderate rate of protein turnover, while adipose tissue has a lower turnover rate compared to the other tissues mentioned.

Correct Answer: C

Rationale: The correct answer is C: amino acids. Proteins are broken down by digestive enzymes into amino acids before being absorbed in the small intestine. Amino acids are the building blocks of proteins and are the form in which they are primarily absorbed. Choice A (fatty acids) is incorrect as fatty acids are the end products of fat digestion, not protein digestion. Choice B (disaccharides) is incorrect because disaccharides are sugars that are broken down into monosaccharides, not proteins. Choice D (polypeptides) is incorrect as proteins are broken down into amino acids and not absorbed as polypeptides.

Correct Answer: D

Rationale: Negative nitrogen balance occurs when the body loses more nitrogen than it gains. This imbalance is often seen in conditions like anorexia in older adults, where insufficient protein intake leads to muscle breakdown and negative nitrogen balance. Choices A, B, and C do not typically lead to negative nitrogen balance as seen in anorexia in older adults.

Correct Answer: C

Rationale: Chylomicrons are the lipoproteins responsible for transporting dietary fat from the intestines to various tissues, including the liver. VLDL carries lipids synthesized in the liver, LDL transports cholesterol to tissues, and HDL helps transport cholesterol away from tissues to the liver for excretion. Therefore, in the context of carrying fat from a meal just consumed to the liver, chylomicrons are the correct choice.