Correct Answer: A

Rationale: Bile salts are essential for emulsifying fats in the body. They break down fats into smaller droplets, increasing the surface area for enzymes to work on during digestion. Cholecystokinin is a hormone that stimulates the release of bile and pancreatic enzymes, but it is not directly involved in emulsification. Chyme is the semi-fluid mass of partly digested food that moves from the stomach to the small intestine and does not play a role in emulsifying fats. Trypsin is an enzyme produced by the pancreas that acts on proteins, not fats.

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: A

Rationale: The correct answer is 'tissue and plasma.' Protein turnover involves the continuous exchange of proteins between body tissues and the bloodstream (plasma) as part of normal metabolic processes. This process ensures a balance in protein levels throughout the body. Choices B, C, and D are incorrect as they do not represent the primary sites for protein turnover in 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.

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.