Which statement about voltage-gated ion channels is true?

Which statement about voltage-gated ion channels is true?

• A. They are activated by changes in transmembrane voltage gradient and are not real receptors
• B. They require ligand binding to open
• C. They are always open
• D. They are intracellular enzymes

Answer: (A)

Voltage-gated ion channels open or close in response to changes in the membrane’s electrical potential, not because a chemical messenger binds to them. They have a voltage-sensing region, often with positively charged residues, that detects depolarization of the membrane. When the voltage becomes more positive, this sensing region moves in a way that opens the pore to allow specific ions to pass. That voltage-driven gating is what makes them true voltage-gated channels, separate from ligand-gated receptors that require a chemical to bind in order to open. They are not always open; at rest the channel is closed, and after opening there can be inactivation or closing as the membrane repolarizes, which helps shape the timing of signals like action potentials. They are not intracellular enzymes; their main role is to form a selective ion-conducting pore in the membrane. This is why the statement that they are activated by changes in transmembrane voltage and are not real receptors best captures their function.

Voltage-gated ion channels open or close in response to changes in the membrane’s electrical potential, not because a chemical messenger binds to them. They have a voltage-sensing region, often with positively charged residues, that detects depolarization of the membrane. When the voltage becomes more positive, this sensing region moves in a way that opens the pore to allow specific ions to pass. That voltage-driven gating is what makes them true voltage-gated channels, separate from ligand-gated receptors that require a chemical to bind in order to open.

They are not always open; at rest the channel is closed, and after opening there can be inactivation or closing as the membrane repolarizes, which helps shape the timing of signals like action potentials. They are not intracellular enzymes; their main role is to form a selective ion-conducting pore in the membrane. This is why the statement that they are activated by changes in transmembrane voltage and are not real receptors best captures their function.