Cell Membrane Structure

• What do membranes control?


  What passes through them
• What do membranes surround?


  • All cells
  • in eukaryotic cells, many of the organelles are surrounded by membranes too
• What do cell-surface membranes surround?


  cells
• What are cell-surface membranes?


  Partially permeable membranes which surround cells and are a barrier between the cell and its environment, controlling which substances enter and leave the cell
• How permeable are cell-surface membranes?

  partially permeable - they let some molecules through but not others
• How can substances move across the cell -surface membrane?

  by diffusion, osmosis or active transport
• What do the membranes around organelles do?


  Divide the cell into different compartments - they act as a barrier between the organelle and the cytoplasm
• Give a detail about the membranes around organelles?


  they are partially permeable and control what substances ENTER and LEAVE the ORGANELLE
• What is the same for all cell membranes?


  the basic structure of all cell membranes
• what are all cell membranes composed of?


  Lipids (mainly phospholipids), proteins and carbohydrates (attached to proteins or lipids)