MARIETTA BIOL 309 - Chapter 12 Membrane Transport

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PowerPoint PresentationSlide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Membrane Transport 1Not responsible for:Nernst Equation, other than to know what it’s used for.Chapter 12 Membrane TransportQuestions in this chapter you should be able to answer:Chapter 12: 2-14, 16, 17, 19, 20, 21A, B, 22, 23Membrane Transport 2To what are membranes permeable?Where are membrane transport proteins found?Aquaporin transporters can facilitate H2O transport in some cellsMembrane Transport 3How do we describe the properties of membrane transport proteins?1. Symmetry of transport2. Mechanism of transportTransport symmetryMembrane Transport 43. Energy requirementsWhat defines ‘active’transport?What potential sources of energy for active transport?Concentration gradientsATPLightElectrical attractionMembrane Transport 5What is “membrane potential”What ions are commonly involved?-- Na+, K+, fixed ionsOutside Insidelow [ K+] High [K+]High [ Na+] Low [Na+]Read text of Figure 12-21pg 399Movement of K+ through the‘K Leak Channel’ establishes the cell’s ‘resting potential’-- concentration gradient-- electrical attraction-- -20 to -200 mAinsideoutsideMembrane Transport 6What are examples of transport coupled to electrochemical gradients?Na+ gradientsH+ gradientscalled 2O active transport What is an electrochemical gradient?concentration gradient+membrane potentialECG can drive or impede transportMembrane Transport 7What are the properties and functions of the Na-pump (Na/K pump)-- 3 Na+ out for 2 K+ inWhat are its…Symmetry?Mechanism?Energy requirement?What are its functions?maintenance of tonicitymaintenance of the Na+ gradientQuestion 12-2, pg 395Na/K pumpMembrane Transport 8How can cells alter membrane potentialand respond to its changes?-- ‘gated’ ion channelsNerve impulse; muscle contraction-- Voltage-gated and ligand-gatedSense of hearing;Plant movements-- Mechanically-gate channelsDirurnal cycling;Phototaxis-- Light-gated channelsMembrane Transport 9How is a nerve impulse generated and transmitted?A nerve impulse is an altered membrane potential= “action potential”Wave-like movementElectrodes can show movementof the action potentialMembrane Transport 10The cellular foundation of “neurobiology” -- the giant neuron of the squidUsed to study factors that affect action potential -- e.g., effect of [Na+]Membrane Transport 11An action potential can be studied experimentally?“Voltage clamping” can be used to manipulate membrane potential-- & study effectsStimulating electrode:-- alters membrane potentialMeasuring electrode:-- measures current (ion) flowVoltage-gated ion gates respondThreshold potentialRefractory periodMeasure currentSet (‘clamp’)membrane potentialSchematic of Voltage Clamp DeviceaxonStimulatingvoltageMembrane Potential (mV)Membrane Transport 12How can the properties of different ion channels be studied?Patch ClampingCan measure current through a single channelQuestion 12-4, p 405Membrane Transport 13How does change in membrane potential effect ion channels?How do ion channels create an action potential?voltage-gated Na+ channels-- 3 statesvoltage-gated K+ channels-- 2 statesclosed open closedState of K+ChannelsState of Na+ChannelsMembrane Transport 14Why does the action potential propagate along the cell membrane?ActionPotentialMembrane Transport 15How is an action potential passed between neurons?Structure of the synaptic complexSynaptic vesiclesMembrane Transport 16What happens when an action potential reaches the synaptic complex?Presynaptic membrane Post-synaptic membrane Voltage-gated Ca++ channels Ligand-gated Na+ channels Exocytosis of vesicles Voltage gated Na+ channelsSynaptic SignallingMembrane Transport 17How can neurons process multiple signals?-- excitatory synapses-- inhibitory synapsesMembrane Transport 18Adapted form question 19-19.The inside of endosomes is acidic, which is achieved by the presence of a H+ pump in the endosome membrane. The endosome membrane also contains a transporter which pumps Cl- into the endosome. If a mutation eliminates the Cl- pump, acidification of the endosome is impaired.A, Draw a diagram of the endosome showing the two transporters and the movement of ions.B. Why does a mutation to the Cl- pump impair endosome acidification?C. Could a Ca++ pump substitute for the Cl- pump? Why or why


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