Correct Answer: D

Rationale: The correct answer is D, amylase. Amylase is an enzyme produced by the salivary glands that initiates the digestion of carbohydrates in the mouth. Pepsin (choice A) is produced in the stomach to digest proteins, trypsin (choice B) is produced in the pancreas to digest proteins, and sucrase (choice C) is produced in the small intestine to break down sucrose. Therefore, choices A, B, and C are incorrect in the context of an enzyme secreted by the salivary glands.

Correct Answer: D

Rationale: The correct answer is D: Hydrochloric acid. Hydrochloric acid in the stomach plays a crucial role in converting pepsinogen into its active form, pepsin, which is necessary for digesting proteins. Bile (Choice A) is involved in the emulsification of fats, not in the activation of pepsinogen. Gastrin (Choice B) is a hormone that stimulates the secretion of gastric acid but does not directly activate pepsinogen. Secretin (Choice C) is a hormone that regulates the pH of the duodenum but is not responsible for the activation of pepsinogen.

Correct Answer: D

Rationale: The correct answer is D: Catabolism. Catabolism involves the breakdown of body proteins into amino acids to be used as energy when there is an inadequate dietary intake. Choices A and B, deamination and transamination, involve the removal and transfer of amino groups, respectively, but not the breakdown of body proteins. Choice C, transcription, is a process in genetics where DNA is used to create mRNA, not related to breaking down body proteins.

Correct Answer: D

Rationale: The correct answer is the amino group. Amino acids consist of an amino group (NH2), a carboxyl group (COOH), a hydrogen atom, and a variable side chain attached to a central carbon atom. The amino group is essential for the formation of proteins. The carboxyl group is not the base component but another important functional group in amino acids. Carbon chain and radicals are not specific chemical structures that form the base component of an amino acid.

Correct Answer: A

Rationale: The correct answer is the amino group. Amino groups are functional groups found in amino acids, which are the building blocks of proteins. These groups contain nitrogen and are essential for the structure and function of proteins. The carboxyl group (choice B) contains carbon, oxygen, and hydrogen, while the peptide bond (choice C) is a covalent bond formed between amino acids in a protein chain. The side chain (choice D) refers to the unique chemical structure attached to the central carbon of an amino acid and varies among different amino acids, but it does not specifically contain nitrogen.