**Question:** Beta cells of pancreas produce:

**Core Concept**: Beta cells are part of the islets of Langerhans in the pancreas and are responsible for producing and releasing insulin.

**Why the Correct Answer is Right**: Beta cells are specialized endocrine cells that secrete insulin, a peptide hormone that plays a crucial role in regulating blood glucose levels. Insulin promotes glucose uptake in target cells, particularly in the liver, muscle, and adipose tissue, and inhibits gluconeogenesis and glycogenolysis in the liver, thereby maintaining glucose homeostasis.

**Why Each Wrong Option is Incorrect**:

A. Alpha cells (correct answer): These cells also reside in the islets of Langerhans but secrete glucagon, a hormone that raises blood glucose levels by stimulating glycogenolysis and gluconeogenesis in the liver.

B. Chymotrypsin: This is an enzyme produced in the pancreas that aids in digestion, not a hormone or part of the endocrine system.

C. Gastrin: Produced by G cells in the stomach, gastrin stimulates gastric acid secretion and is unrelated to glucose regulation.

D. Insulin: As mentioned earlier, insulin is produced by beta cells to regulate glucose levels, not a wrong option.

**Clinical Pearl**: A deficiency or excess of insulin can lead to severe disorders, such as type 1 diabetes mellitus (insulin deficiency) and diabetes mellitus type 2 (insulin resistance). Adequate insulin production is essential for maintaining glucose homeostasis and preventing hyperglycemia or hypoglycemia.

**Correct Answer**: B. Insulin

This answer is correct because insulin is produced by beta cells of the pancreas to regulate blood glucose levels by facilitating glucose uptake in target cells and inhibiting gluconeogenesis in the liver. Insulin is crucial for glucose homeostasis and preventing hyperglycemia or hypoglycemia.