4.2: Diffusion Flashcards
Diffusion
The net movement of particles from an area of higher concentration to an area of lower concentration
Net movement
Particles will diffuse in both ways but the net movement is the overall movement which will be to an area of lower concentration
Diffusion occurs … conc. gradient
down a conc. gradient
Diffusion is a … process
passive
Passive process
no energy needed for it to happen
Diffusion across cell membranes
Particles can diffuse across cell membranes as long they can move freely through the membrane
(non-polar and small)
Simple diffusion
When molecules diffuse directly through a membrane
Facilitated diffusion uses
carrier proteins and protein channels
Facilitated diffusion
When particles diffuse through carrier proteins or channel protein down a concentration gradient from a higher to a lower concentration
Which particles diffuse by facilitated diffusion
Polar molecules/ charged particles
bigger particles
Facilitated diffusion is a … process
passive
Carrier proteins
Move larger molecules across membranes and different carrier proteins move different molecules
Carrier protein process
3 steps
large molecules attaches to a carrier protein in the membrane
then the protein changes shape
this releases the molecules on the opposite side of the membrane
Channel proteins
Form pores in the membrane for charged particles to diffuse through and different channel proteins move different charged particles
Simple diffusion
depends on
3
concentration gradient
thickness of the exchange surface
surface area
