Question

What kinds of molecules pass through a cell membrane most easily? What properties of the molecules and the membrane allow this to happen?

Answer 1

Small and simple

Explanation:

Small and simple molecules like water, `H_2O`, can pass through the cell membrane easily as it is partially permeable.

The cell membrane can filter out unimportant molecules that the cell does not need to use, and also only lets small molecules pass through. Some molecules like water are small enough to diffuse through the cell membrane and into the cell. Also, other things may include oxygen `(O_2)` and carbon dioxide gas `(CO_2)`.