Question

Which of the following is permeable to all substances?

• A. Cell wall
• B. Cell membrane
• C. Plasma membrane
• D. None of these

Answer 1

The correct option is A Cell wall

During short distance transport (SDT) the molecules have to cross 2 boundaries- cell wall and cell membrane (plasma membrane). Cell wall is freely permeable to all substances. Cell membrane is selectively permeable. Small non polar molecules (oxygen, nitrogen, carbondioxide) can easily pass through the cell membrane. Uncharged polar molecules- small (water, ammonia, glycerol) and large (glucose, sucrose) can partially pass through the cell membrane. Ions (${\mathrm{Na}}^{+}$, $K^{+}$, ${\mathrm{Cl}}^{-}$ etc) cannot easily pass through the cell membrane. The cell membrane is freely permeable to water.