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level: Diffusion and membrane permeability

Questions and Answers List

level questions: Diffusion and membrane permeability

QuestionAnswer
Define diffusionThe net movement of particles from an area of high concentration to an area of lower concentration, down a gradient.
How long does diffusion takeUntil particles are evenly distributed
Is diffusion a passive or an active processa 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 phospholipidsSmall, non-polar molecules like oxygen and carbon dioxide
How does concentration gradient affect diffusionthe higher it is, the faster the rate of diffusion
How does the thickness of the exchange surface affect diffusionthe thinner the exchange surface, the faster the rate
How does surface area affect diffusionthe larger the surface are, the faster the rate
How does temperature affect diffusionthe warmer it is, the faster the rate of diffusion because particles have more kinetic energy so they move faster
How does temperature affect membrane permeabilityAt 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