Answer:
(b) Voltage gated
Explanation:
The cell membrane acts as a barrier that separates two aqueous media of different composition, the extracellular and the intracellular, regulating its composition. Most of the liposoluble drugs and solutes, when not ionized, directly cross the cell membrane through a passive diffusion process, which facilitates the passage of the medium where it is more concentrated to the one that is more diluted. The difference in concentration between the two media is called the concentration gradient, and diffusion will continue until this gradient is eliminated. According to Fick's law, the speed of this process will be much faster the higher the concentration gradient and the liposolubility of the molecule and the smaller its size.
More hydrophilic molecules, such as ions, are immiscible in membrane lipids and pass through specific specific transport mechanisms. In some cases, ions pass through hydrophilic pores called ion channels, and in others a favor of their concentration gradient is transported by binding to the transporter or transporter proteins. Both transport systems are passive and therefore do not consume energy. The great advantage is that the ion channels allow the flow of ions through a much higher speed than that of any other biological system. The flow of ions through each channel can be measured as an electric current, which is capable of producing rapid changes in membrane potential.
