Lecture5Spr08 - ANNOUNCEMENTS *First essay due date Friday...

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Unformatted text preview: ANNOUNCEMENTS *First essay due date Friday Feb 22 (NOT Wed Feb 20). *Paper on which essay is to be based, and questions to be addressed in the essay, will be available at the end of this week. *Graded Quiz will be handed back at the end of the lecture (alphabetically, last name A on left facing front, Z on right.) Review : Freeze fracture -> TEM (not SEM). Review : Transport of glucose into gut epithelial cell and then out on other side into blood stream: *This is important to understand. What are the roles of the two transporters and where does the energy come from? * 3D appearance comes from heavy metal shadowing at an angle. Cartoon Movie: Na/K ATPase and ion gradients across the plasma membrane (a07-02-biological_energy.swf ) Review: Selective movement of ions leads a membrane potential *Cells inside is ~70 mV negative relative to outside (= ~200,000 v/cm!) *This potential is due mostly to non-gated (constitutively open) K+ channels. Fig. 11.7 Gated ion channels are the principle underlying conduction of nervous impulses *The opening and closing of ion channels can be controlled by small molecules (e.g. neurotransmitters, like acetyl choline) or by voltage across the membrane. *This is the basis of conduction of nerve impulses. Fig. 23.6 *The Frst step in this process is depolarization of the membrane by opening of Na+ channels. *See Ch 23, ig. 23.9 for outline of steps in conduction of action potential along nerve. (You do not need to know this.) *A charged helix senses the membrane potential, moving slightly in response to change in voltage, opening channel. *A separate domain of the protein (ball in diagram) blocks the channel after initial opening. *This is Na+ channel, but principle is same for other voltage-gated channels. Fig. 23.7 Molecular model for voltage-gated ion channels (Na+ channel as example) The cytoskeleton has three components Fig. 17.2 *There is some communication between these three systems, but largely they are independent. Fig. 17.3 Cytoskeleton organization responds to signals *Microflaments and microtubules are highly dynamic, but intermediate flaments are not. *Simple example oF signaling: trypsinizing cultured cells -> they round up (thereFore dramatic change in cytoskeleton) in seconds to minutes. Cytoskeleton in the apical part of an intestinal epithelial cell *This is an example of how the structure of a cell is maintained by the cytoskeleton. *Paradigm for cell biology: isolate the type of cell or part of a cell in which a structure or protein is enriched . Apply what is learned in this tractable system to other cells....
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This note was uploaded on 09/30/2008 for the course BIOBM 432 taught by Professor Vogt during the Spring '08 term at Cornell University (Engineering School).

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Lecture5Spr08 - ANNOUNCEMENTS *First essay due date Friday...

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