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.

Correct Answer: C

Rationale: Lipase is an enzyme that specifically breaks down lipids (fats) during the process of digestion, converting them into fatty acids and glycerol. This is why option C is the correct answer. Although option D is partially correct, it's less specific than option C. Lipase does not break down carbohydrates or proteins, so options A and B are incorrect.

Correct Answer: C

Rationale: Metabolism is the correct answer as it refers to the sum of all chemical processes that occur within living cells to maintain life and health. Physiology (Choice A) is the study of how living organisms function but does not specifically refer to cellular chemical processes. Digestion (Choice B) is the process of breaking down food in the body, not the overall cellular processes. Nutrition (Choice D) is the process of obtaining and consuming food necessary for health and growth, but it does not encompass all cellular processes related to sustaining life and health.

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: B

Rationale: The correct answer is B: Supply energy. The primary function of macronutrients such as carbohydrates, fats, and proteins is to supply energy for various bodily functions. Choices A, C, and D are incorrect because while regulating metabolic processes, maintaining homeostasis, and controlling cellular activity are essential functions in the body, they are not the primary roles of macronutrients. Macronutrients mainly serve as a source of energy to support daily activities and bodily functions.