Cholecystokinin (CCK) is produced in the:

Correct Answer: A

Rationale: Cholecystokinin (CCK) is produced in the duodenum, not the stomach, pancreas, or liver. It is released in response to the presence of food in the duodenum, where it plays a crucial role in regulating digestive processes by stimulating the release of bile from the gallbladder and enzymes from the pancreas. Therefore, the correct answer is the duodenum (Choice A). Choices B, C, and D are incorrect because CCK is not produced in the stomach, pancreas, or liver.

Correct Answer: D

Rationale: The correct answer is D: Catabolism. Catabolism involves the breakdown of body proteins into amino acids to be used as energy when there is an inadequate dietary intake. Choices A and B, deamination and transamination, involve the removal and transfer of amino groups, respectively, but not the breakdown of body proteins. Choice C, transcription, is a process in genetics where DNA is used to create mRNA, not related to breaking down body proteins.

Correct Answer: C

Rationale: Gluconeogenesis mainly occurs in the liver. It is a process where glucose is synthesized from non-carbohydrate sources such as amino acids and glycerol. The liver is the primary site for gluconeogenesis due to the presence of key enzymes and substrates required for this process. Muscles do not play a significant role in gluconeogenesis, making choice A incorrect. The pancreas is involved in the regulation of blood sugar levels through insulin and glucagon but is not the primary site for gluconeogenesis, so choice B is incorrect. The spleen is not a major organ involved in glucose metabolism, making choice D incorrect.

Correct Answer: A

Rationale: Mucus is produced by the salivary glands to moisten food and aid in swallowing. Additionally, the intestinal glands secrete mucus to protect the lining of the intestines. The other choices, esophageal glands, pineal gland, and islets of Langerhans, are not involved in the production of mucus in the digestive system.

Correct Answer: C

Rationale: The correct answer is C: mucus. Mucus forms a protective barrier that prevents the stomach and intestine from digesting themselves. Pepsinogen (choice A) is an inactive form of pepsin, a digestive enzyme, and does not protect the stomach lining. Bile (choice B) aids in the digestion and absorption of fats but does not protect the stomach lining. Fat (choice D) is a nutrient and energy source; it does not play a role in protecting the stomach and intestine from self-digestion.

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: Bacteria found in the colon are important because they synthesize important vitamins, such as vitamin K. This aids in the body's overall health and functioning. Choice B is incorrect because absorption primarily occurs in the small intestine, not the colon. Choice C is incorrect as the synthesis of minerals is not a primary function of colon bacteria. Choice D is incorrect as the digestion process mainly occurs in the stomach and small intestine.

Correct Answer: B

Rationale: The correct answer is B: Carbohydrates and fats. Carbohydrates are the body's primary and most efficient source of energy, providing fuel for daily activities. Fats are also a significant energy source, especially during times of prolonged or intense exercise. Proteins are primarily used for building and repairing tissues, not as a major energy source. Vitamins and minerals are essential for various bodily functions but do not serve as direct sources of energy.

Correct Answer: D

Rationale: The correct answer is D: Hydrochloric acid. Hydrochloric acid in the stomach plays a crucial role in converting pepsinogen into its active form, pepsin, which is necessary for digesting proteins. Bile (Choice A) is involved in the emulsification of fats, not in the activation of pepsinogen. Gastrin (Choice B) is a hormone that stimulates the secretion of gastric acid but does not directly activate pepsinogen. Secretin (Choice C) is a hormone that regulates the pH of the duodenum but is not responsible for the activation of pepsinogen.