membraneTransport

membraneTransport - Membrane Transport IN OUT Membranes...

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Membrane Transport IN OUT
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Membranes separate the contents of the cell from the extracellular space and keep the contents of the organelles separate from the cytoplasm.
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How do biomolecules get from one compartment to another? Membrane fusion and budding. Through the membrane: Simple Diffusion Passive transport Active transport
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Membrane fusion Endocytosis: taking stuff into the cell Exocytosis: secreting stuff from the cell
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Endocytosis Phagocytosis: “eating” the cell membrane extends and surrounds food. The vesicle is internalized and eventually fuses with the lysosome where the food is “digested” Pinocytosis: “drinking” extra cellular fluid fills a pit in the surface of the cellular membrane. No extensions form. Receptor mediated endocytosis: Ligands bind to a receptor on the cell surface and the ligand receptor complex are internalized.
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Exocytosis Secretion of membrane bound proteins. Secretion of proteins for extra cellular space. Regeneration of cell membrane Waste diposal from lysosomes.
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Through the membrane Most carriers are integral membrane proteins that span the membrane
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Most carriers are integral membrane proteins that span the membrane
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Passive Transport Nonmediated: Transport occurs through simple diffusion Mediated: Transport uses a specific transport protein. Uses chemical gradient for “energy”. Facilitated diffusion leads to much higher transport rates than simple diffusion.
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Energetics of Passive Membrane Transport The free energy of a solute depends on concentration In membrane transport, solute moves from one side to the other A out in [ ] [ ] 2 1 ln C G RT C ∆=
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Considering going from out in if [C] in < [C] out , then ΔG < 0 → favorable if [C] in > [C] out , then ΔG > 0 → not favorable Favorable process if solute travels down the concentration gradient from high to low concentration [ ] [ ] 2 1 ln C G RT C ∆=
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Unfavorable process (against gradient) would require energy input Charged molecules are also affected by membrane potential (electrochemical gradient across the membrane) Positive side Negative side ψ ∆= [] ln in out C G RT ZF C
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This note was uploaded on 07/07/2010 for the course CHEM 237 taught by Professor Elisabethdaub during the Fall '10 term at Waterloo.

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membraneTransport - Membrane Transport IN OUT Membranes...

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