15 - Facilitated Diffusion: Passive Transport aided by...

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Facilitated Diffusion: Passive Transport aided by Proteins In facilitated diffusion , transport proteins speed the passive movement of molecules across the plasma membrane Channel proteins provide corridors that allow a specific molecule or ion to cross the membrane Channel proteins include: Aquaporins, for facilitated diffusion of water Ion channels that open or close in response to a stimulus ( gated channels ) The need for Energy in Active Transport Active transport moves substances against their concentration gradient Active transport requires energy, usually in the form of ATP Active transport is performed by specific proteins embedded in the membrane Active transport allows cells to maintain concentration gradients that differ from their surroundings The sodium-‐potassium pump is one type of active transport system How Ion Pumps Maintain Membrane Potential Membrane potential is the voltage difference across a membrane Voltage is created by differences in the distribution of positive and negative ions
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This note was uploaded on 11/19/2010 for the course BIO 121 taught by Professor Smith during the Spring '10 term at McCormick Theological Seminary.

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15 - Facilitated Diffusion: Passive Transport aided by...

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