Question

Which of the following statements is true for protein hormones?

• A. They do not enter target cells
• B. They interact with membrane-bound receptors and generate second messengers inside the cell
• C. They interact with intracellular receptors and generate second messengers inside the cell
• D. Intracellular receptor-hormone complex interacts with the organism's genome

Answer 1

Answer: (A), (B)

The correct options are
A They do not enter target cells
B They interact with membrane-bound receptors and generate second messengers inside the cell

Hormones that are too large or too polar to cross the plasma membranes of their target cells include all of the peptide and glycoprotein hormones, as well as the catecholamine hormones epinephrine and norepinephrine. These hormones bind to receptor proteins located on the outer surface of the plasma membrane — the hormones do not enter the cell but generate second messengers. The interaction between the hormone and its receptor activates mechanisms in the plasma membrane that increase the concentration of the second messengers within the target cell cytoplasm.