What is the role of pepsin in digestion?

Correct Answer: C

Rationale: The correct answer is C: Digesting proteins. Pepsin is a digestive enzyme produced in the stomach that specifically breaks down proteins into smaller peptides. It works optimally in acidic environments, aiding in the digestion of proteins consumed in the diet. The other choices are incorrect because pepsin does not play a role in digesting carbohydrates (A), fats (B), or nucleic acids (D). Carbohydrates are primarily broken down by enzymes like amylase, fats by lipase, and nucleic acids by nucleases. Thus, pepsin's main function is to digest proteins in the stomach.

Correct Answer: B

Rationale: Secretin is the correct answer because it is not a hormone that directly affects the stomach. Gastrin stimulates gastric acid secretion, GIP enhances insulin release, and neurotensin regulates gastric motility. Secretin primarily targets the pancreas and liver, stimulating the release of bicarbonate-rich pancreatic juice. This hormone does not have a direct major effect on the stomach like the other options. Therefore, Secretin is the exception among the listed GIT hormones affecting the stomach.

Correct Answer: C

Rationale: Rationale: 1. Gastric phase starts when food enters the stomach. 2. Chemoreceptors detect bolus composition to initiate gastric secretions. 3. This detection triggers release of gastric juices for digestion. 4. Neural stimulation also occurs during gastric phase, but not exclusively. 5. Contractility increases during gastric phase for mixing and churning. In summary, choice C is correct as chemoreceptors detect bolus composition during the gastric phase, while the other choices are incorrect because they do not accurately reflect the physiological processes during this phase.

Correct Answer: C

Rationale: The correct answer is C: small intestine. Primary carcinoma is least common in the small intestine compared to the other choices. This is because the small intestine has a lower incidence of cancer compared to the esophagus, stomach, and colon. Factors contributing to this lower incidence include less exposure to carcinogens, a relatively smaller surface area, and less common inflammatory conditions that can lead to cancer development. Additionally, the small intestine has a more rapid turnover of cells, reducing the likelihood of cancerous mutations accumulating. Therefore, the small intestine is the least common site for primary carcinoma among the options provided.

Correct Answer: B

Rationale: The correct answer is B because the normal concentration of bilirubin in the plasma is about 0.8 gm%, which is a commonly accepted fact in medicine. Bilirubin is a product of hemoglobin breakdown and is typically measured in the blood to assess liver function and detect certain medical conditions. A, C, and D are incorrect: A: Myenteric plexus controls GIT motility, not secretion. C: Submucosal plexus controls GIT secretion, not motility. D: Pepsinogen activation needs hydrochloric acid (HCl) in the stomach, not calcium.