The major food digested by gastric secretions is

Correct Answer: C

Rationale: The correct answer is C: protein. Gastric secretions primarily consist of hydrochloric acid and pepsin, which break down proteins into smaller peptides. This process is essential for protein digestion in the stomach. Choices A, B, and D are incorrect because fats are primarily digested in the small intestine with the help of bile, starch is broken down by amylase in the mouth and small intestine, and nucleic acids are digested in the small intestine by nucleases. Therefore, protein is the major food digested by gastric secretions due to the presence of pepsin and hydrochloric acid in the stomach.

Correct Answer: D

Rationale: The correct answer is D, cholecystokinin. Cholecystokinin is released in response to the presence of fatty acids and amino acids in the duodenum, stimulating the secretion of the enzymatic component of pancreatic juice. Gastric inhibitory polypeptide (A) regulates insulin release, not pancreatic enzyme secretion. Secretin (B) stimulates bicarbonate secretion from the pancreas, not enzyme secretion. Gastrin (C) stimulates gastric acid secretion, not pancreatic enzyme secretion. Therefore, cholecystokinin is the correct hormone for stimulating the enzymatic component of pancreatic juice secretion.

Correct Answer: A

Rationale: The correct answer is A: stomach and pancreas. Firstly, protein digestion starts in the stomach where pepsinogen is converted to pepsin, breaking down proteins. Secondly, the pancreas secretes enzymes like trypsin and chymotrypsin into the small intestine to further break down proteins. The other choices are incorrect because the salivary glands primarily produce enzymes for carbohydrate digestion, while the small intestine is more involved in absorbing nutrients rather than producing protein-digesting enzymes.

Correct Answer: B

Rationale: The correct answer is B: Bile salts emulsify fat, aiding in fat digestion. Bile salts are amphipathic molecules that break down large fat globules into smaller droplets, increasing the surface area for enzymes to act upon. This enhances fat digestion and absorption. Choice A is incorrect because pepsinogen conversion is not a function of bile salts. Choice C is incorrect as bile salts are essential for digestion. Choice D is incorrect as bile salts specifically target fats, not all macromolecules.

Correct Answer: C

Rationale: The correct answer is C: gastric acid and pepsin. Gastric acid (hydrochloric acid) creates an acidic environment for pepsin, an enzyme that breaks down proteins. Bicarbonate and histamine do not directly facilitate protein digestion. Mucus protects the stomach lining. Gastric lipase aids in fat digestion, not protein digestion.