Question

As a rule, lipid-soluble hormones require a transport protein to circulate in the bloodstream. What is the function of the transport protein?

A. It increases the ability of hormones to move through the blood.
B. It is required for binding of a hormone to its receptor.
C. It helps the hormone to cross cell membranes and enter the target cells.
D. It decreases hormone solubility in blood plasma.

Answer 1

The function of the transport protein is to help the hormone cross cell membranes and enter the target cells. Therefore, the correct option is c.

Step-by-step explanation:

The function of the transport protein is to C. help the hormone to cross cell membranes and enter the target cells.

Lipid-soluble hormones, such as steroid hormones, are hydrophobic and cannot dissolve in the watery bloodstream. Transport proteins bind to these hormones, keeping them soluble in the blood and facilitating their transport to target cells. Once at the target cell, the hormones are released from the carrier protein and diffuse across the membrane to bind to intracellular receptors inside the cell, regulating gene transcription and affecting the cell's activities.