Diffusion is a means of passive transport. It results from the thermal, random movement of molecules.
Rate of Diffusion =
gradient x temp X surface
area · solubility
distance · sq. rt of the molecular mass
Six things influence the rate of diffusion:
Size of molecule involved
Distance the molecule has to travel
Solubility of the molecule
Surface area of the membrane over which the molecule can work
There are three main types of diffusion: simple, channel, and facilitated diffusion.
Simple diffusion is when a small,
In simple diffusion, a hydrophobic molecule
An example of simple diffusion is osmosis.
Hydrophilic molecules cannot participate in simple diffusion because
would move into the hydrophobic region of the membrane and be rejected.
Saturation does not occur with simple diffusion or with
The bigger the gradient, the greater the transport of materials.
Channel diffusion is another type of passive
Facilitated diffusion is a type of passive transport that is dependent on single transport protein carriers.
These protein carriers operate on a bind, flip, release mechanism.
Facilitated diffusion is non-diffusional because the molecule moves along with the carrier.
Saturation occurs in facilitated diffusion because not enough
carriers may be available to handle all the free solute molecules.
The rate of movement may reach a maximum.
How can you tell the difference between a carrier and a channel
Manipulate the concentrations of the molecules and see if saturation occurs.
If saturation does occur, then you know that you are dealing with a carrier protein.
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