Question

Insulin is a hormone that regulates blood sugar by binding to its receptor, insulin receptor tyrosine kinase. How does insulin’s behavior differ from steroid hormone signaling, and what can you infer about its structure?

a) Insulin acts on intracellular receptors; it has a hydrophobic structure
b) Insulin acts on cell-surface receptors; it has a hydrophilic structure
c) Insulin acts on intracellular receptors; it has a hydrophilic structure
d) Insulin acts on cell-surface receptors; it has a hydrophobic structure

Answer 1

Insulin acts on cell-surface receptors and differs from steroid hormone signaling by having a hydrophilic structure that cannot cross the cell membrane, unlike the hydrophobic steroid hormones.

Step-by-step explanation:

Insulin's behavior differs from steroid hormone signaling in that it acts on cell-surface receptors rather than intracellular receptors. Since insulin is not lipid-soluble it cannot diffuse across the cell membrane like steroid hormones. Therefore, insulin binds to receptors on the surface of the target cell.

Specifically, insulin binds to the insulin receptor tyrosine kinase, activating mechanisms such as the translocation of Glut-4 transporters to the plasma membrane to facilitate glucose uptake into cells. This indicates that insulin has a hydrophilic structure. Hence, the correct answer to how insulin's behavior differs from steroid hormone signaling and the inferred structure of insulin is (b) Insulin acts on cell-surface receptors; it has a hydrophilic structure.