| Define diffusion | The net movement of particles from an area of high concentration to an area of lower concentration, down a gradient. |
| How long does diffusion take | Until particles are evenly distributed |
| Is diffusion a passive or an active process | a passive process as particles can diffuse across plasma membranes, as long as they can move freely through the membrane |
| What molecules are able to diffuse easily through the phospholipids | Small, non-polar molecules like oxygen and carbon dioxide |
| How does concentration gradient affect diffusion | the higher it is, the faster the rate of diffusion |
| How does the thickness of the exchange surface affect diffusion | the thinner the exchange surface, the faster the rate |
| How does surface area affect diffusion | the larger the surface are, the faster the rate |
| How does temperature affect diffusion | the warmer it is, the faster the rate of diffusion because particles have more kinetic energy so they move faster |
| How does temperature affect membrane permeability | At higher temperatures, lipids have more kinetic energy and are packed together more loosely increasing the fluidity. This increases membrane permeability. |
| How does lipids effect the membrane permeability? | - when long/saturated, they have a high melting point, which decreases fluidity
- when short/unkinked, molecules can pack together more tightly
- when short/unsaturated, they have a low melting point, which increases fluidity as double bonds create kinks, meaning molecules are packed together more loosely |
| How does cholesterol effect the membrane permeability? | - high levels at the body temperature, means that cholesterol interacts with the tails of phospholipids decreasing fluidity
- lower levels at the body temperature can make membrane too fluid, increasing the risk of cell bursting |
| How do you investigate the effect of temperature | -using beetroots, the higher the temperature the darker the pigment released as cell surface membrane becomes disrupted |
