effects of temperature on membrane permeability

• Cell membranes are affected by temperature - it affects how much the phospholipids in the bilayer can move, which affects membrane structure and permeability.
• Temperatures below 0 °C

  • The phospholipids don't have much energy, so they can't move very much.
  • They're packed closely together and the membrane is rigid.
  • But channel proteins and carrier proteins in the membrane denature, increasing the permeability of the membrane.
  • Ice crystals may form and pierce the membrane, making it highly permeable when it thaws.
• Temperatures between 0 and 45 °C

  • The phospholipids can move around and aren't packed as tightly together - the membrane is partially permeable.
  • As the temperature increases the phospholipids move more because they have more energy - this increases the permeability of the membrane.
• Temperatures above 45 °C

  • The phospholipid bilayer starts to melt (break down) and the membrane becomes more permeable.
  • Water inside the cell expands, putting pressure on the membrane.
  • Channel proteins and carrier proteins in the membrane denature so they can't control what enters or leaves the cell - this increases the permeability of the membrane