Factors Affecting Membrane Structure & Permeability
- The permeability of cell membranes is affected by different factors or conditions, such as:
- Temperature
- Solvent concentration
Temperature
- Proteins and lipids (the major components in cell membranes) are both affected by temperature
- As temperature increases, lipids become more fluid
- This increased fluidity reduces the effectiveness of the cell membrane as a barrier to polar molecules, meaning polar molecules can pass through
- At higher temperatures, any diffusion taking place through the cell membrane will also occur at a higher speed (due to increased kinetic energy)
- Changes in membrane fluidity are reversible
- If temperatures decrease, the lipids will return to their normal levels of fluidity)
- At a certain temperature (often around 40°C) many proteins (including those in cell membranes) begin to denature
- This disrupts the membrane structure, meaning it no longer forms an effective barrier
- As a result, substances can pass freely through the disrupted membrane
- This process is irreversible
Solvent concentration
- Organic solvents can increase cell membrane permeability as they dissolve the lipids in the membrane, causing the membrane to lose its structure