Question

the plasma membrane is much more permeable to k+ than to na+. why?
the na+-k+ pumps transport more k+ into cells than na+ out of cells.
there are many more k+ leak channels than na+ leak channels in the plasma membrane.
there are many more voltage - gated k+ channels than voltage - gated na+ channels.
ligand - gated cation channels favor a greater influx of na+ than k+.

Explanation:

• The \(Na^{+}-K^{+}\) pump transports 3 \(Na^{+}\) out of the cell and 2 \(K^{+}\) into the cell, so it does not explain higher permeability of \(K^{+}\) (first option wrong).
• Voltage - gated channels are mainly involved in action potential generation (not the resting - state permeability, so third option wrong).
• Ligand - gated cation channels (if non - selective) would not explain the higher permeability of \(K^{+}\) (fourth option wrong).
• Leak channels are responsible for the resting - state permeability. There are more \(K^{+}\) leak channels than \(Na^{+}\) leak channels in the plasma membrane, which makes the plasma membrane more permeable to \(K^{+}\).

Answer:

There are many more \(K^{+}\) leak channels than \(Na^{+}\) leak channels in the plasma membrane.