Cell Membrane structure

• compare The basic structure of all cell membranes, including cell-surface membranes and the membranes around the cell organelles of eukaryotes


  , is the same.
• what do membranes do?

  control what passes through them
• what are all cells surrounded by

  Membranees

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

  cells
• what are cell-surface membranes a barrier between?

  The cell and its environment
• what do cell-surface membranes control?

  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
• what do the membranes around organisms act as?

  a barrier between the organelle and the cytoplasm
• Give details about the membranes aroundd organelles?

  • partially permeable
  • control what substances enter and leave the organelle
• what structure do cell membranes have?

  a fluid mosaic structure
• What was the fluid mosaic model suggested to describe?


  the arrangement of molecules in the membrane
• in the model,what do phospholipid molecules do?

  form a continuous , double layer (BILAYER)
• Why is the bilayer 'fluid'?

  because the phospholipids are constantly moving
• what molecules are present within the bilyer?

  cholesterol molecules
• what are scattered through the bilayer?

  proteins
• why is it mosaic?

  proteins are scattered through the bilayer, like tiles in a mosaic
• which proteins are scattered throughout the bilayer?


  Channel proteins and carrier proteins , which allow large molecules and ions to pass through te membrane

  • receptor proteins
• what do receptor proteins on the cell-surface membrane allow the cell to do?

  Detect chemicals released from other cells

  • the chemicals SIGNAL to proteins on LIVER CELLS, which tells the cells to ABSORB GLUCOSE
• What are some proteins able to do?

  Move sideways through the bilayer, while others are fixed in position
• what are glycoproteins?

  proteins with a polysaccharide chain attached
• what are glycolipids?

  lipids with a polysaccharide chain attached
• what does the phospholipid bilayers allow?


  the movement/diffusion of non-polar/lipid-soluble substances
• what does the phospholipid bilayer prevent?


  movement /diffusion of polar/charged/lipid-insoluble substances