factors affecting membrane structure

• temperature

  phospholipids in a cell membrane are constantly moving.

  = when temperature is increased the phospholipids will have more kinetic energy and will move more.

  • this makes a membrane more fluid and it begins to lose it's structure.
  • if temperature continues to increase the cell will eventually break down completely.
  • carrier and channel proteins in the membrane will be denatured at higher temperatures. These proteins are involved in transport across the membrane so as they denature, membrane permeability will be affected.
• solvents

  = water, a polar solvent, is essential in the formation of the phospholipid bilayer. The non-polar tails of the phospholipids are orientated away from the water, forming a bilayer with a hydrophobic core. The charged phosphate heads interact with water, helping to keep the bilayer intact.
• solvents:

  • many organic solvents are less polar than water- eg: alcohol
  • organic solvents will dissolve membranes disrupting cells.- this is why alcohols are used in antiseptic wipes, they dissolve the membranes of bacteria, killing them.
  • Pure or very strong alcohol solutions are toxic and destroy cells in the body.
  • less concentrated alcohols won't dissolve membranes but still cause damage. The non-polar alcohol molecules can enter the cell membrane and the presence of these molecules between the phospholipids disrupts the membrane.
• solvents:

  • when the membrane becomes disrupted it becomes more fluid and more permeable. Some cells need intact cell membranes for specific functions. Eg: transmission of nerve impulses by neurones. when neuronal membranes are disrupted nerve impulses are no longer transmitted as normal.