How does the cell membrane affect the contents of a cell?
Protection and Transport.
The Cell Membrane protects the organelles inside the cell and keeps them from sliding around your body uselessly. It gives the cell shape.
It also allows some transport. Active and Passive transport move ions and vital molecules into and out of the cell. This is allowed because the Cell membrane is semi-permeable. (Only allows certain things in and out in relation to the balance of concentration of ions).
As mentioned above, the Cell's ability to be semi permeable balances the concentration ions inside the cell.