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Question	Answer
3 major routes by which substances can cross membranes?	Diffusion through aqueous pores. Dissolving in the lipid portion of the membrane. Carrier mediated or facilitated diffusion.
What can pass through pores and channels in the lipid layer?	Water and other polar molecules
Polar molecules are those with an.........charge distribution. They have positive and negative ends.	uneven
Pore size is about ......in diameter?	10 Angstroms. Therefore any molecule bigger than this cannot pass through the membrane by this route.
What substances diffuse through the lipid membrane?	Gases (oxygen, carbon dioxide) Steroid hormones Fatty acids Glycerol and other alcohols
With simple diffusion and dissolving in the lipid membrane the rate of movement is in ........proportion to the concentration gradient across the membrane.	direct.
However, with carrier mediated (facilitated) diffusion there is ........increase in rate of movement at a higher concentration gradient.	NO. i.e. the rate of movement reaches a plateau.
There are ......molecules which become saturated at higher concentrations.	CARRIER
What process maintains the concentration difference across the membrane?	ACTIVE TRANSPORT
The active transport systems are known as...	Membrane pumps - they pump a substance from one side of the membrane to the other.
What does the active transport system need in order to work?	ATP (ENERGY)

Membrane function

	Created by Morgan Morgan almost 12 years ago