Question

Which of the following molecules can pass through the membrane freely?

• A. Sucrose
• B. Glycerol
• C. Ammonia
• D. Water

Answer 1

The correct option is D Water

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.