Correct Answer: B

Rationale: Pepsinogen is converted into its active form, pepsin, by hydrochloric acid in the stomach. Hydrochloric acid helps in unfolding the pepsinogen molecule to transform it into pepsin, which is crucial for protein digestion. Therefore, the correct answer is hydrochloric acid (choice B). Enterokinase (choice A) is an enzyme produced in the small intestine that activates trypsinogen into trypsin, not pepsinogen. Gastric lipase (choice C) is an enzyme that digests fats, not involved in converting pepsinogen to pepsin. Pancreatic lipase (choice D) is an enzyme produced by the pancreas that aids in breaking down fats in the small intestine, not part of the process of pepsin activation.

Correct Answer: B

Rationale: Cholecystokinin (CCK) is the correct answer. It is the hormone responsible for stimulating the gallbladder to contract and release bile to aid in fat digestion. Gastric lipase (Choice A) is an enzyme that breaks down fats in the stomach, not a hormone involved in gallbladder function. Vitamin D (Choice C) is important for calcium absorption and bone health, but it is not directly related to gallbladder function. Enterokinin (Choice D) is a peptide hormone that affects smooth muscle contractions in the gastrointestinal tract, but it is not specifically responsible for stimulating the gallbladder to release bile.

Correct Answer: D

Rationale: The correct answer is D, Maltose. A disaccharide is formed when two monosaccharides are joined together. Glucose, fructose, and galactose are all monosaccharides, not disaccharides. Therefore, they are not examples of disaccharides.

Correct Answer: A

Rationale: The correct answer is A, Milk. Milk is considered a complete protein as it contains all the essential amino acids required by the body. Soy (choice B) is also a complete protein, containing all essential amino acids. Sesame seeds (choice C) and sweet potato (choice D) are not complete proteins as they lack one or more essential amino acids needed by the body.

Correct Answer: A

Rationale: The correct answer is A: act as buffers. Amino acids can act as buffers by helping to maintain the pH balance in the body. Choice B is incorrect because amino acids do not primarily facilitate glucose storage. Choice C is incorrect as amino acids do not regulate the heartbeat. Choice D is also incorrect because amino acids do not control the level of blood cholesterol.