Question

Where is it likely that you will find the receptor molecules for chemical signals?

• A. In the nucleus of target cells
• B. In the interstitial fluid surrounding target cells
• C. In the cell membrane of target cells
• D. In the cytoplasm of target cells

Answer 1

Answer: (A), (C), (D)

The correct options are
A In the nucleus of target cells
C In the cell membrane of target cells
D In the cytoplasm of target cells

Lipophilic hormones bind to receptors which may either be present in the cytoplasm or the nucleus of target cells. Some steroid hormones then bind to very specific receptor proteins in the cytoplasm, and then move as a hormone-receptor complex into the nucleus. Other steroids travel directly into the nucleus before encountering their receptor proteins, irrespective of whether the steroid finds its receptor in the nucleus or translocates with its receptor to the nucleus from the cytoplasm. Hormones that are too large or too polar to cross the plasma membranes, bind to receptor proteins located on the outer surface of the plasma membrane — the hormones do not enter the cell.