Which enzyme is secreted by the salivary glands?

Correct Answer: D

Rationale: The correct answer is D, amylase. Amylase is an enzyme produced by the salivary glands that initiates the digestion of carbohydrates in the mouth. Pepsin (choice A) is produced in the stomach to digest proteins, trypsin (choice B) is produced in the pancreas to digest proteins, and sucrase (choice C) is produced in the small intestine to break down sucrose. Therefore, choices A, B, and C are incorrect in the context of an enzyme secreted by the salivary glands.

Correct Answer: D

Rationale: The correct answer is D, amylase. Amylase is an enzyme produced by the salivary glands that initiates the digestion of carbohydrates in the mouth. Pepsin (choice A) is produced in the stomach to digest proteins, trypsin (choice B) is produced in the pancreas to digest proteins, and sucrase (choice C) is produced in the small intestine to break down sucrose. Therefore, choices A, B, and C are incorrect in the context of an enzyme secreted by the salivary glands.

Correct Answer: D

Rationale: The correct answer is D: 20. There are 20 different amino acids that combine to form proteins in the human body. Each amino acid has a unique side chain that determines its properties. Choices A, B, and C are incorrect as they do not represent the total number of different amino acids found in human proteins.

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: A

Rationale: Glucose serves as a primary source of energy for the body, especially for the brain and muscles. Choice B is incorrect because glucose itself is not responsible for transporting oxygen to cells. Choice C is incorrect as glucose is converted to glycogen, not the other way around. Choice D is incorrect as glucose itself does not play a direct role in maintaining body weight.

Correct Answer: B

Rationale: In a low-carbohydrate diet, fats become the primary source of calories as carbohydrate intake is restricted. Proteins can contribute to caloric intake but are not the primary source in a low-carbohydrate diet. Carbohydrates are intentionally limited in this diet, so they do not supply most of the calories. Vitamins are essential nutrients but do not provide calories.

Correct Answer: C

Rationale: The correct answer is C: 'presence of food in the stomach.' Gastric secretions are stimulated when food enters the stomach, triggering nerve and hormonal responses. This process prepares the stomach for digestion. Choices A, B, and D are incorrect because ingesting water, swallowing reflex, and the closing of the pyloric sphincter do not directly stimulate the release of gastric secretions.

Correct Answer: B

Rationale: Cholecystokinin (CCK) is the hormone responsible for stimulating the gallbladder to contract and release bile into the small intestine. Secretin primarily acts on the pancreas to stimulate the secretion of bicarbonate-rich fluid. Gastrin functions in the stimulation of gastric acid secretion, while Gastric inhibitory polypeptide (GIP) plays a role in inhibiting gastric acid secretion and stimulating insulin release.

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.