IMG_0004_NEW_0008 - / Cell Structure and Function should...

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/ Cell Structure and Function should read the relevant sections in your textbook for a more detailed description of membrane proteins and carbohydrates and their functions. We have so far only considered diffusion and osmosis as ways by which materials enter and leave cells. Two other very important processes help transport materials across membranes. Both these processes differ from simple diffusion and osmosis in that they require a protein molecule (usually an integral membrane protein) to effect this transfer. Differences between the various processes are shown in one composite diagram at the bottom of page 11. Diffusion moves molecules from high to low concentrations, the way the 2nd law of thermodynamics predicts. Facilitated diffusion also moves material down a concentration gradient but requires a transport protein in the membrane. In active transport, substances are moved against a concentration gradient, i.e. from a low to a high concentration, with the help of a transport protein in the membrane. Since this
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This note was uploaded on 12/29/2011 for the course MBB 222 taught by Professor Briscoe during the Fall '10 term at Simon Fraser.

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