Correct Option
The correct option is 1 and 3 only.
Explanation
Insulin is a peptide hormone secreted by the β-cells of the Islets of Langerhans in the pancreas. It plays a critical role in glucose homeostasis by regulating the metabolism of carbohydrates, fats, and proteins. Its primary function is to lower blood glucose levels (hypoglycemic effect).
Statement-wise Analysis
- Statement 1 is Correct: Insulin acts mainly on hepatocytes (liver cells) and adipocytes (adipose tissue cells). It enhances cellular glucose uptake and utilization in these tissues, thereby moving glucose from the blood into the cells.
- Statement 2 is Incorrect: Insulin stimulates (does not inhibit) glycogenesis, which is the conversion of glucose into glycogen for storage in the liver and muscles. Simultaneously, it inhibits glycogenolysis (breakdown of glycogen) and gluconeogenesis (formation of glucose from non-carbohydrate sources).
- Statement 3 is Correct: By promoting the rapid movement of glucose from the blood into hepatocytes and adipocytes and stimulating its conversion into glycogen, insulin decreases blood glucose levels. Consequently, it prevents hyperglycemia (high blood sugar).
Key Takeaway
Insulin is an anabolic hormone that lowers blood glucose by increasing cellular uptake and promoting glycogenesis, while Glucagon is a catabolic hormone that raises blood glucose by promoting glycogenolysis and gluconeogenesis.