Question

What do voltage-gated Na⁺ channels permit to pass through their pores? Are they specific to Na⁺/K⁺? What do they open and close in response to? Do they adopt conformational changes, similar to that of the delayed rectifier K⁺ channels?

Answer 1

Voltage-gated Na⁺ channels allow only sodium ions to pass through and are triggered to open or close by changes in the membrane potential. They operate through conformational changes similar to but distinct from delayed rectifier K⁺ channels, playing a key role in action potentials.

Step-by-step explanation:

Voltage-gated Na⁺ channels are specialized proteins in cell membranes that permit the passage of sodium ions (Na⁺) through their pores. These channels are highly specific to Na⁺ ions and do not typically allow other ions such as potassium (K⁺) to pass through. They open and close in response to changes in the membrane potential, specifically when the electrical charge inside the cell membrane becomes less negative. These channels do undergo conformational changes, similar to those observed in delayed rectifier K⁺ channels, but with distinct timing and gating mechanisms. The activation of the Na⁺ channels occurs rapidly when the membrane potential crosses a certain threshold (e.g., -55 mV), which allows a rush of Na⁺ ions into the cell. This plays a crucial role in the initiation and propagation of action potentials in excitable cells like neurons and muscle cells.