diffusion

what is diffusion?

the net movement of ions/molecules from an area of high concentration to an area of low concentration

is diffusion an active or passive process?

passive - does not require energy

what is facilitated diffusion?

diffusion (the net movement of ions/molecules from an area of high concentration to an area of low concentration) involving carrier proteins

name the two types of proteins involved in facilitated diffusion:

• channel proteins

• carrier proteins

what are the key features of channel proteins?

• intrinsic

• ions can pass through

• fluid (usually water) filled protein channel

what are the key features of carrier proteins?

• have a specific BINDING site

• carrier protein rotates once molecule has bound to the protein

compare and contrast channel and carrier proteins:

name 4 factors which affect the rate of diffusion:

• membrane thickness

• temperature

• surface area

• concentration gradient

how does membrane thickness affect the rate of diffusion?

• the thicker the membrane, the lower the rate of diffusion

• as the diffusion distance is further

how does temperature affect the rate of diffusion?

• the higher the temperature, the higher the rate of diffusion

• as at a higher temperatyure, particles willl have more kinetic energy

• so will be able to move around faster

how does surface area affect the rate of diffusion?

how does the concentration gradient affect the rate of diffusion?

• the steeper the concentration gradient, the higher the rate of diffusion

• this can be maintained by a good blood/air supply, which transports substances to and from the membrane

• (otherwise diffusion rate would decrease over time as equilibrium is reached)