How can a membrane be permeable to one substance while being impermeable to another substance?

It varies due to their polarities.

Explanation:

Remember, a membrane is a semi-permeable membrane. There are some substances that can cross the membrane and others have to take different route. It all comes down to their polarity. If we were to examine a membrane made of phospholipid bilayers, one side of it has hydrophilic heads and the inside has hydrophobic tails. The membrane is therefore polar, allowing polar substances to enter in and out of the cell. Non polar substances, such as water have to take a different route, through special proteins called aquaporins.

answer: accepted answer: aquatic animals use the oxygen dissolved in water to carry out respiration. since the amount of dissolved oxygen in water is low as compared to the amount of oxygen in the air, therefore the rate of breathing in aquatic animals is much faster than it is in terrestrial animals.

explanation: