Correct Answer: B

Rationale: Carbohydrates have a protein-sparing effect, meaning that adequate carbohydrate intake can prevent the use of protein for energy. Glycerol, nitrogen, and fatty acids do not have a protein-sparing effect. Glycerol is a component of fats and oils, nitrogen is a component of proteins, and fatty acids are used primarily as an energy source.

Correct Answer: D

Rationale: The correct answer is D, rennin. Rennin is the enzyme in infants responsible for coagulating milk, which aids in the digestion process. Choice A, casein, is a milk protein and not an enzyme. Choices B and C, pepsinogen and trypsin, are digestive enzymes but are not specifically involved in coagulating milk in infants.

Correct Answer: B

Rationale: A nursing infant receives antibodies from its mother through the absorption of antibodies present in breast milk. Choice A is incorrect as anabolism and catabolism refer to metabolic processes, not the transfer of antibodies. Choice C is incorrect as the infant does not need to synthesize antibodies but directly receives them. Choice D is incorrect because while genetic inheritance plays a role in the immune system, in this case, the direct transfer of antibodies occurs through breast milk.

Correct Answer: A

Rationale: Branched chain amino acids, such as leucine, isoleucine, and valine, are essential in preventing muscle breakdown. Therefore, they may be particularly important for a patient with cancer-related malnutrition, where maintaining muscle mass is crucial. Marasmus is a severe form of malnutrition characterized by energy deficiency, not specifically related to cancer. Cardiovascular disease and severe depression do not have a direct correlation with the need for branched chain amino acids to prevent muscle breakdown.

Correct Answer: A

Rationale: The correct answer is the radical group (R-group) because it is the unique side chain that differentiates each amino acid. The amino group (choice B) and carboxyl group (choice C) are functional groups common to all amino acids but do not make them unique. The peptide bond (choice D) is the bond formed between amino acids in a protein chain, not the group that makes each amino acid unique.