different components of cell membranes & their roles

• What do different components of cell membranes have?


  different roles
• What do phospholipid molecules have?


  • a hydrophilic head
  • a hydrophobic tail
• how are the phospholipid molecules arranged in the bilayer?


  The molecules automatically arrange themselves into a bilayer- the heads face out towards the water on either side of the membrane
• what is the CENTRE OF THE BILAYER like?


  the centre of the bilayer is hydrophobic so the membrane doesn't allow water-soluble substances through it- it acts as a barrier to these dissolved substances
• give an example of water-soluble substances?


  ions
• what is the role of phospholipids in the cell membrane?


  form a barrier to dissolved substances
• what does cholesterol do in the membrane?


  cholesterol gives the membrane stability
• what is cholestoral a type of?


  LIPID
• Is cholesterol a carb, protein or lipid?


  LIPID
• Where is cholesterol present?


  in ALL CELL MEMBRANES (except bacterial membranes)
• where are cholesterol molecules in the membrane?


  • Cholesterol molecules fit between the phospholipids
• what do cholesterol molecules bind to?


  the hydrophobic tails of the phospholipids, causing them to pack more closely together.

  This restricts the movement of the phospholipids, making the membrane less fluid and more rigid.
• What does cholesterol help to maintain?


  the shape of animal cells (which do not have cell walls)

  this is particularly important for cells that are not supported by other cells, eg red blood cells which float free in the blood
• give an example of a type of cell which is not supported by other cells?


  eg red blood cells, which float free in the blood