Which statement describes intracellular receptor activity?

• A. It binds ligands only at the cell surface.
• B. It cannot influence gene expression.
• C. It cannot bind DNA.
• D. It binds a ligand and can bind DNA, unlike membrane receptors.

Answer: (D)

Intracellular receptors respond to signals that cross the cell membrane and often regulate gene expression directly. After a lipophilic ligand binds inside the cell, the receptor can act as a transcription factor and bind DNA to modulate transcription. That makes the statement about binding a ligand and being able to bind DNA, in contrast to membrane receptors, the best description.

Ligands that are hydrophobic cross the membrane easily, which is why intracellular receptors are placed inside the cell rather than at the surface. This contrasts with receptors located on the cell membrane that typically initiate signaling cascades without directly interacting with DNA.