Which statement correctly describes transmembrane receptors?

Which statement correctly describes transmembrane receptors?

• A. They are integral components of the cell membrane with an extracellular ligand-binding domain and an intracellular signal-transmitting domain.
• B. They are extracellular only and do not bind ligands.
• C. They are located only in the nucleus.
• D. They do not bind ligands.

Answer: (C)

Transmembrane receptors are proteins that span the cell membrane. They have an extracellular region that binds signaling molecules and an intracellular region that relays the signal inside the cell. This arrangement lets an outside signal cause a change inside the cell, often triggering kinase activity or second-messenger cascades. That makes the best description one that calls them integral membrane proteins with both an extracellular ligand-binding domain and an intracellular signal-transmitting domain. They are not simply extracellular, they are not confined to the nucleus, and they do bind ligands to initiate signaling.

Transmembrane receptors are proteins that span the cell membrane. They have an extracellular region that binds signaling molecules and an intracellular region that relays the signal inside the cell. This arrangement lets an outside signal cause a change inside the cell, often triggering kinase activity or second-messenger cascades.

That makes the best description one that calls them integral membrane proteins with both an extracellular ligand-binding domain and an intracellular signal-transmitting domain. They are not simply extracellular, they are not confined to the nucleus, and they do bind ligands to initiate signaling.