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diffusion (net movement of particles from a region of higher concentration…
diffusion
net movement of particles from a region of higher concentration to a region of lower concentration
passive process
continues until a concentration equilibrium occurs between the two areas
simple diffusion - diffusion in the absence of a barrier or membrane
diffusion across membranes
can only happen if membrane is permeable to particles e.g. non-polar molecules diffuse through freely
hydrophobic interior of membrane repels substances with a positive or negative charge
polar molecules diffuse through at a very slow rate - small molecules pass through easier than large ones
facilitated diffusion
diffusion across a membrane through protein channels
membranes with protein channels - selectively permeable
rate of facilitated diffusion
temperature
concentration gradient
membrane surface area
thickness of membrane
number of channel proteins present
passive process
factors affecting rate of diffusion
temperature
higher temperatures mean a higher rate of diffusion
particles have more kinetic energy and move at higher speeds
concentration difference
greater difference in concentration between two regions means faster rate of diffusion
overall movement from higher concentration to lower concentration is larger
factors affecting rate of diffusion across membranes
surface area
larger the area of an exchange surface the higher the rate of diffusion
thickness of membrane
thinner the exchange surface the higher the rate of diffusion