Voltage-gated ion channels underlie the function of electrically excitable cells, such as nerve and muscle cells. Which statement is true about voltage-gated ion channels?1. Voltage-gated ion channels involve a conformational change of the transmembrane protein, which occurs in response to membrane voltage that changes the channel's permeability to ion flow through the channel.2. Voltage-gated ion channels vary in terms of how rapidly they respond to changes in membrane potential. 3. Voltage-gated ion channels open and close in response to changes in membrane potential.4. All of these choices are correct.