What triggers the release of cholecystokinin (CCK)?

Correct Answer: B

Rationale: The correct answer is B: Presence of fat in the duodenum. Cholecystokinin (CCK) is released in response to the presence of fat in the duodenum to aid in digestion by stimulating the release of bile from the gallbladder and enzymes from the pancreas. Options A, C, and D are incorrect because CCK is specifically released in response to the presence of fat in the duodenum, not food in the stomach, acid chyme in the ileum, or bile in the gallbladder.

Correct Answer: A

Rationale: The correct answer is A: Villi. Villi are small fingerlike projections in the intestine that increase the surface area for nutrient absorption. Goblets (choice B) are mucus-secreting cells in the intestines. Lacteals (choice C) are lymphatic vessels in the small intestine that absorb dietary fats. Polyps (choice D) are abnormal tissue growths.

Correct Answer: B

Rationale: The absorption of most nutrients occurs in the small intestine. This is where digested food is broken down further and absorbed into the bloodstream through the intestinal walls. The large intestine primarily absorbs water and electrolytes, while the stomach mainly aids in digestion by breaking down food with gastric juices. The mouth is responsible for the initial mechanical breakdown of food through chewing and the enzymatic action of saliva, but absorption does not occur there.

Correct Answer: C

Rationale: Probiotics are live bacteria that are beneficial for gut health and are often taken as supplements. They are not indigestible carbohydrates (Choice A), antibiotics (Choice B), or commercial fiber supplements (Choice D). Probiotics contain live strains of good bacteria that help maintain a healthy balance in the gut microbiome.

Correct Answer: A

Rationale: The correct answer is A: monosaccharides. When macronutrients like carbohydrates are digested, they are broken down into simpler forms. Carbohydrates are broken down into monosaccharides, proteins into amino acids, and fats into fatty acids. Therefore, the end products of carbohydrate digestion are monosaccharides. Choices B, C, and D are incorrect because polysaccharides are larger carbohydrate molecules, enzymes are not the end products of digestion but rather aid in the process, and cholesterol is not a direct end product of macronutrient digestion.