cells08-Transport2-2009 - Lect 8 Transport 2: Channels;...

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Unformatted text preview: Lect 8 Transport 2: Channels; Nerves GlucoseGlucose-Na+ Symport Protein In the previous slide, what is the source of energy to move glucose against its concentration gradient? ECB3 12-17 Movement of glucose against its concentration gradient. ATP used directly B. ATP used indirectly used indirectly C. Na+ electrochemical gradient D. A & B E. B & C A. GlucoseGlucose-Na+ Symport Protein CoCo-transport Carrier Proteins Uses energy from electrochemical potential gradient to move molecule against its concentration gradient. transported (the co-transported ion is comoved WITH its conc. gradient) ECB3 12-17 continue video video 12.3 Na+-ATP pump maintains the Na+ ECG that drives the simultaneous transport of glucose against its concentration gradient. Against Conc. Gradient Modified from ECB2 12-13 Intestinal Epithelial Cells low [sugar] into high [sugar] Na+-glucose Symport Protein low [sugar] into high [sugar] high [sugar] into low [sugar] Lodish et al., 1995 Cooper 13.32 Bio 106 Fall 2009 Professor Owen 1 Lect 8 Transport 2: Channels; Nerves Na+/K+ ATPase Pump Facilitated Diffusion high [sugar] into low [sugar] low [sugar] Movie 12.4 Glucose Transport by Intestinal Epithelial Cells Summary Na+-glucose Symport Protein ATP P ADP Cooper 13.32 What is the energy to move glucose INTO the intestinal cell (against its concentration gradient)? What is the energy to move glucose OUT of the intestinal cell (into extracellular fluid)? A. B. C. D. ATP B. Na+ gradient C. Diffusion D. No energy A. ATP Na+ gradient Simple diffusion (no energy) Diffusion through transport protein (no energy) Bio 106 Fall 2009 Professor Owen Modified from ECB3 12-18 2 Lect 8 Transport 2: Channels; Nerves CarrierCarrier-mediated solute transport in plant and animal cells Channels – A Different Type of Facilitated Diffusion Cooper 13.18 • Water-filled holes within a protein allow ions Waterto pass through the membrane • Selective for a specific ion for each channel • Rapid transport – 10,000,000 ions / sec able to pass through ECB3 12-19 • No protein binding 2003 Nobel Prize in Chemistry water • Aquaporins are membrane water channels that control the water contents of cells. • They facilitate the transport of water across the membrane. • Widely distributed in all kingdoms. kingdoms. • Several diseases, such as congenital cataracts and nephrogenic diabetes insipidus, are connected to the impaired function of these channels. • Pores are impermeable to charged ions. http://www.ks.uiuc.edu/Research/aquaporins/ Aquaporins – A Special Channel • Water channel proteins that accelerate the osmotic flow (conc. gradient) of water • Some cells move water across the membrane very rapidly membrane very rapidly – (it is normally relatively slow) – ex: kidney cells that reabsorb water from urine Gated Ion Channels • Hydrophilic pore that is ion-selective ion• Able to open and close • 1 million ions / second can pass through ECB3 12-21 Bio 106 Fall 2009 Professor Owen 3 Lect 8 Transport 2: Channels; Nerves K+ Channel Protein 3 Types of Gated Ion Channels 1 2 3 ECB3 12-20 ECB3 12-25 Venus Flytrap Trigger hair opens mechanically gated ion channels that create an electrical current to rapidly close the trap. Supper time! ECB3 12-22 Patch Patch Clamping Technique Neher & Sakmann – Nobel Prize (Medicine) 1991 Modified from ECB3 12-23 Patch Clamp Data Inner Ear organ of Corti Acetylcholine given to a patch of muscle cell briefly ECB3 12-24 opens the ion channel, then it closes. Bio 106 Fall 2009 Professor Owen 4 Lect 8 Transport 2: Channels; Nerves Inner Ear Normal sensory hairs StressStress-activated ion channels Damaged sensory hairs due to 120db sound exposure (= amplified rock music at 4-6 ft) 4organ organ of Corti within the cochlea Preston and Hawkins, Kresge Hearing Research Institute, University of Michigan Animations 12.6 & 12.7 12.7 ECB2 12-25 Electrochemical Gradient Predict how this + charge is established across the membrane A. B. C. D. Greatest energy potential ECB2 12-8 simple diffusion passive (facilitated) transport (facilitated) transport H+ ATP pump Na+/K+ ATP pump Nernst Equation The flow of any ion through a membrane channel protein is driven by the electrochemical gradient for that ion. This gradient represents the combination of two influences: the voltage gradient and the concentration gradient of the ion across the membrane. Membrane Potentials E = equilibrium potential in volts Co RT E = ZF ln C i R=gas constant T=absolute temp Z=ion valency F=Faraday const. Able to calculate the theoretical membrane potential if the ratio of the internal to external ion concentrations is known. Modified from ECB3 12-28 Bio 106 Fall 2009 Professor Owen 5 Lect 8 Transport 2: Channels; Nerves K+ Leak Channels ECB3 12-29 Rat cortical astrocytes (glial cells found in the brain) Neurons VoltageVoltage-gated Na+ Channel Membrane at rest start here Na+ moves into cell • Nerves function by a traveling wave of electrical excitation known as an action potential. • Action potentials are the direct consequence of voltagevoltagegated cation channels ECB 12-31 3 Modified from ECB2 12-33 Membrane Potentials ++ + + + + + Membrane Potentials (6000 Na+ pass through/ms) ++++ + Cooper 13.21 + ++ Cooper 13.21 Bio 106 Fall 2009 Professor Owen 6 Lect 8 Transport 2: Channels; Nerves Brief pulse of current Membrane becomes partially depolarized Propagation of an Action Potential Along an Axon [Na+] inside<<outside Action of voltage-gated Na+ channels. No additional stimulus will open the channels until resume the closed state (refractory) animation 12.8 ECB3 12-35 ECB3 12-39 ECB3 12-39 Propagation of an Action Potential Along an Axon Neurons Neurons transmit chemical signals across synapses. ECB3 12-40 Neurotransmitter at Synaptic Cleft Cooper 13.22 Science Visualization Challenge Award Winner animation 12.9 Bio 106 Fall 2009 Professor Owen 7 ...
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