Question

bio-201 topic 2: cell physiology & tissues
practice it
what makes the cell membrane selectively permeable to na+ and k+ ions?
concentration gradients of other ions
cholesterol molecules embedded in the membrane
ion channels that are specific to each ion
transporter proteins that actively pump ions across the membrane
physical size of the ions

Explanation:

Cell membranes have ion - specific channels. These channels allow certain ions like Na+ and K+ to pass through while restricting others. Concentration gradients of other ions do not directly determine Na+ and K+ permeability. Cholesterol molecules mainly affect membrane fluidity. Transporter proteins actively pump ions but are not the main factor for selective permeability in the sense of allowing passage. The physical size of the ions is not the key determinant of selective permeability for these ions. Ion - specific channels are the main mechanism for selective permeability to Na+ and K+ ions.

Answer:

C. Ion channels that are specific to each ion