Correct Answer: A

Rationale: Protein catabolism increases in conditions like severe burns because the body breaks down muscle protein to provide energy for healing. Severe obesity does not necessarily increase protein catabolism; instead, it is more related to excessive fat accumulation. Hypothyroidism may lead to a decrease in metabolic rate but does not directly increase protein catabolism. Food allergies trigger an immune response to specific foods but do not directly impact protein catabolism.

Correct Answer: B

Rationale: The correct answer is B. The classification of the 20 common amino acids is not based on the properties of their side chains, but rather on the structure of their amino and carboxyl groups. These groups are consistent among all amino acids, while the side chains, also known as R groups, are what vary and give each amino acid its unique properties. Choice A is correct because proteins are indeed composed of amino acids. Choice C is incorrect because while the side chains of amino acids can vary, the general structure of an amino acid - a central carbon atom bonded to an amino group, a carboxyl group, a hydrogen atom, and a side chain - is consistent. Choice D is correct because amino acids do polymerize to form long chains called polypeptides, which can then fold into complex shapes to form proteins.

Correct Answer: C

Rationale: The Acceptable Macronutrient Distribution Range (AMDR) for fat suggests that 20% to 35% of total kcalories should come from fat. This range is recommended to maintain good health. Choices A, B, and D are incorrect because they do not fall within the specified range. A lower percentage (10-20%) may not provide enough essential fatty acids, while a higher percentage (30-45%) may increase the risk of health issues associated with excessive fat consumption.

Correct Answer: B

Rationale: The correct answer is B, Coconut oil. Coconut oil is a saturated fat derived from plants and does not contain cholesterol, unlike the other options. Butter (choice A) is an animal-derived saturated fat that contains cholesterol. Eggs (choice C) and fish (choice D) also contain cholesterol, making them incorrect choices. Therefore, coconut oil is the only option that is a saturated fat and does not contain cholesterol.

Correct Answer: C

Rationale: Fat is important in the diet because it provides satiety. Fat slows down digestion and absorption, which helps in making you feel full longer. This feeling of fullness is crucial in controlling food intake and managing weight. Choices A, B, and D are incorrect because fat's main role in providing satiety is related to slowing down digestion, not supplying a constant source of vitamins, speeding up digestion, or stimulating the release of digestive enzymes. While some types of fats can provide certain vitamins, the main purpose of fat in satiety is not vitamin supply.