341lecture19oct23sakai

341lecture19oct23sakai - Cell Biology 341 Friday, October...

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Cell Biology 341 Friday, October 23, 2009 Today: The answers to chapter 7 questions are on WebCT transporters that carry out active transport: “Coupled transporters” use an electrochemic al gradient as the energy source Pumps use ATP or light Last lecture: finished chapter 10 The cell cortex (part of the cytoskeleton) is a network of peripheral proteins attached to transmembrane proteins, which have restricted movement in the lipid bilayer Tight junctions also restrict protein movement Began Chapter 12: transport of charged and large polar molecules across membranes Transporters vs. channel proteins Active transport (against gradient) vs. passive (down the concentration gradient) Facilitated diffusion: the glucose uniport transports glucose by passive transport Ion gradients create a membrane potential across the plasma membrane (outside = +) An electrochemical gradient is the sum of the concentration gradient of an ion plus the membrane potential
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The movement of an ion depends not only on concentration, but also on charge The electrochemical gradient is the sum of the concentration gradient plus the membrane potential Figure 11-4b Force due to concentration gradient only Potential increases the force Potential decreases the force outside inside outside inside Na + Ca ++
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Ion gradients across the plasma membrane (+ charge on the outside) [Na + ] is higher outside animal cells [H + ] is usually higher outside plant, fungal and bacterial cells [Ca ++ ] is higher outside all cells all 3 of these ions will rapidly enter a cell if an
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This note was uploaded on 12/05/2009 for the course BIO 341 taught by Professor Noris during the Fall '09 term at Rhode Island.

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341lecture19oct23sakai - Cell Biology 341 Friday, October...

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