L06 Energetics2011

L06 Energetics2011 - Lecture6Outline...

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Proteins as membrane transporters (Ch 12 ECB) Channel Transporter proteins Facilitated diffusion Active transport (enzyme)  Lecture 6 Outline Cellular Energetics ATP Synthesis Energy carrying molecules Energy Energy Only material presented in lecture will be on exams
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-  Need to get an impermeable molecule across the  membrane - going  WITH  its electrochemical gradient G negative  (will eventually happen but slowly due to low membrane permeability) No input of energy required - Need to get a molecule across the membrane going  AGAINST   its  electrochemical gradient   G positive  -  will not occur spontaneously, must put in energy - Must couple to a  G negative reaction such as: - 1.  - 2. Specialized membrane proteins for transport functions Transport problems faced by cells: ATP hydrolysis Electrochemical ion gradient
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Two broad classes of transmembrane proteins that facilitate transport Channel protein: Channel protein: Hydrophilic pore Hydrophilic pore (No  (No  conformational change  conformational change  during transport) during transport) Transporter protein = carrier protein Transporter protein = carrier protein Undergoes conformational change during transport Undergoes conformational change during transport ECB 12-3
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Each organelle in a eukaryotic cell has its own unique set of  transporters and channels ECB 12-5
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Transport can be passive or active  Active transport  requires energy to move a molecule against its electrochemical gradient ( G+) Passive transport  moves a molecule down its electrochemical gradient ( G-) and so does not require energy electrochemical We will discuss each of these (left to right) ECB 12-4
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Channels  -   - Passive transport down electrochemical gradient     Channel-mediated Channel-mediated passive transport passive transport Common for transport of small ions across membranes Move transported molecule in either direction depending on direction of EC gradient Channels discriminate based on size and charge ECB 12-3
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Channel structure Regulation - open or closed; switch rapidly between states e. g. Na +  channels and nerve conduction Selective, discrimination based on charge and size (see ECB 12- 19 for K +  channel selectivity)  R groups involved in selectivity Often high rate of transport, up to 10 6  per sec ECB 11-24 Aqueous pore due to polar and charged R groups Always passive transport α -helix or  β -barrel Tradeoff between selectivity and transport rate
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Slower than channels Transfer across membrane driven by  conformational change  in transporter Binding of transported molecule induces conformational change Highly specific because carrier binds transported molecule ECB 12-6 down EC gradient   aka   uniport Transporter-mediated passive transport electrochemical
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This note was uploaded on 02/01/2011 for the course BIO 2020 taught by Professor Kropf during the Spring '11 term at University of Utah.

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L06 Energetics2011 - Lecture6Outline...

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