Cell membranes

• Membranes control what passes through, they have a barrier between the cell and it's environment, controlling which substances enter and leave the cells. They are partially permeable. Some substances can move across the plasma membrane by diffusion, osmosis or active transport and allow cell communication
• The membranes around organelles divide the cell into different compartments and act as a barrier between the organelle and the cytoplasm. This makes different functions more efficient