membrane permeability

• temperature below 0 degrees c -

  • phospholipids don't have much energy so cant move much
  • packed closely together and membrane is rigid
  • channel and carrier proteins deform increasing permeability of the membrane
  • ice crystals may form and pierce the membrane making it highly permeable
• temperatures between 0 and 45 -

  • phospholipids can move around and aren't packed as closely
  • membrane is partially permeable
  • as temp increases phospholipids move more due to more energy
  • increases permeability of the membrane
• temperatures above 45 -

  • phospholipid bilayer starts to melt and membrane becomes more permeable
  • water in the cell expands, puts pressure on the membrane
  • channel and carrier proteins deform so cant control what enters and leaves the cell
  • increases permeability
• Permeability is the ease with which molecules cross biological membranes, either by passive diffusion, active transport, or channel proteins
• 1. surrounding cells in a solvent increase permeability of the cell membrane
  2. because solvents dissolve the lipids in a cell membrane so the membrane loses its structure
  3. some solvents increase cell permeability more than others e.g. ethanol more than methanol
  4. increasing conc of a solvent also increases membrane permeability