Which statement about receptors is true?

Which statement about receptors is true?

• A. They are always located on the cell surface
• B. They are DNA sequences that bind ligands
• C. They are macromolecules that interact with ligands to initiate events
• D. They do not demonstrate specificity

Answer: (C)

Receptors are macromolecules that recognize and bind ligands with high specificity, and that binding triggers cellular events. They aren’t limited to the cell surface; some reside inside the cell and respond to lipophilic signals by altering gene expression or other intracellular processes. This ability to selectively bind a ligand and convert that binding into a response is why receptors are central to signaling and drug action. For example, surface receptors like GPCRs or receptor tyrosine kinases initiate cascades when their ligands bind, while intracellular receptors for steroids modulate transcription. The other statements don’t fit because receptors are not confined to the cell surface, they are not DNA sequences that bind ligands, and they do demonstrate specificity in recognizing their ligands.

Receptors are macromolecules that recognize and bind ligands with high specificity, and that binding triggers cellular events. They aren’t limited to the cell surface; some reside inside the cell and respond to lipophilic signals by altering gene expression or other intracellular processes. This ability to selectively bind a ligand and convert that binding into a response is why receptors are central to signaling and drug action. For example, surface receptors like GPCRs or receptor tyrosine kinases initiate cascades when their ligands bind, while intracellular receptors for steroids modulate transcription. The other statements don’t fit because receptors are not confined to the cell surface, they are not DNA sequences that bind ligands, and they do demonstrate specificity in recognizing their ligands.