Question

Insulin and thyroxine arrive at an organ at the same time. Thyroxine causes an effect on the organ but insulin does not. Why?

a. Insulin is lipid-soluble hormone and thyroxine is not.
b. The target cells in the organ have up-regulated thyroxine.
c. Thyroxine is a local hormone and Insulin is a circulating hormone.
d. Thyroxin inhibits the action of insulin.
e. The organ's cells have receptors for thyroxine but not for insulin.

Answer 1

Insulin and thyroxine have different effects on an organ because the organ's cells have receptors for thyroxine but not for insulin. Thyroxine is a non-steroid hormone that can bind to receptors on the cell membrane, while insulin is a peptide hormone that cannot enter the cell.

Step-by-step explanation:

Insulin and thyroxine have different effects on an organ because the organ's cells have receptors for thyroxine but not for insulin. Thyroxine is a non-steroid hormone that binds to receptors on the outer surface of the cell membrane, activating a signaling pathway that triggers intracellular activity. In contrast, insulin is a peptide hormone that cannot enter the cell, so it cannot directly affect the organ's cells. Therefore, the organ responds to thyroxine but not insulin.