In which part of the alimentary canal does most digestion occur?

Correct Answer: B

Rationale: The correct answer is B: proximal small intestine. Most digestion occurs in the proximal small intestine because it is where the majority of enzymes are secreted to break down food. This section also has a large surface area for absorption of nutrients. The stomach primarily breaks down food with acids, while the distal small intestine and ascending colon focus on absorption of nutrients and water, respectively.

Correct Answer: C

Rationale: The correct answer is C: trypsin. Trypsin is responsible for digesting proteins as it specifically breaks down proteins into smaller peptides. Amylase (A) digests carbohydrates, lipase (B) breaks down fats, and sucrase (D) digests sucrose, a type of sugar. Trypsin is produced by the pancreas and plays a crucial role in protein digestion in the small intestine. Its specificity for proteins makes it the correct enzyme for this function.

Correct Answer: B

Rationale: The primary function of the large intestine is to absorb water and electrolytes from the indigestible food residue passed from the small intestine. This absorption process helps in forming solid waste (feces) and maintaining body fluid balance. Absorbing nutrients (Option A) primarily occurs in the small intestine. Digesting proteins (Option C) mainly takes place in the stomach and small intestine. The secretion of digestive enzymes (Option D) also primarily occurs in the stomach and small intestine, not in the large intestine. Therefore, the correct answer is B.

Correct Answer: C

Rationale: The correct answer is C: absorption of nutrients. The small intestine is responsible for absorbing nutrients from digested food into the bloodstream for distribution to the body's cells. It has specialized structures like villi and microvilli to maximize absorption surface area. Choice A is incorrect because while the small intestine does play a role in digesting fats, it is not its primary function. Choice B is incorrect because the digestion of carbohydrates primarily occurs in the mouth and stomach. Choice D is incorrect as the small intestine does not store bile, but rather receives it from the liver and gallbladder to aid in digestion.

Correct Answer: B

Rationale: The correct answer is B: Stomach. Protein digestion begins in the stomach where the enzyme pepsin is secreted. Pepsin breaks down proteins into smaller peptides. This process is aided by the acidic environment of the stomach. In contrast, the mouth primarily starts the digestion of carbohydrates through the enzyme salivary amylase. The small intestine is where further breakdown and absorption of nutrients occur, not the initial digestion of proteins. The large intestine is mainly responsible for absorbing water and electrolytes, not digestion.