BIOL 302 1st Edition Lecture 19 Outline of Last Lecture I. AntobodiesOutline of Current Lecture I. Membrane transportII. Membrane channelsIII. CarriersIV. pumpsCurrent LectureI. Not all molecules diffuse readily through membranes.II. Transport through membranesThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.III. ChannelA. forms a pore in the membraneB. Carrier1. Changes conformation to allow a solute to bind on one side and release on the other side.2. Some carriers pass solutes from high to low concentration. 3. Some do opposite. The latter are also called “pumps”IV. ThermodynamicsA. Concentration gradients store free energy.1. Transport of a solute from place of high concentration to place of low concentration can be coupled to an energy-requiring process B. Conversely, energy is required to transport a solute from place of low concentration to a place of high concentration.V. Free energy change for transport of substrates across a membraneA. G = RT ln (c2/c1)1. Free-energy change in transporting an uncharged species from side 1, where it is present at the concentration c1, to side 2, where it has the concentration c2.a. R is the gas constant (8.315x10-3 kJ/ mol K).b. T is the temperature in KelvinIII. Free energy change for transport of substrates across a membraneA. G = RT ln (c2/c1)1. Free-energy change in transporting an uncharged species from side 1, where it is present at the concentration c1, to side 2, where it has the concentration c2.a. PASSIVE TRANSPORTa. Does not require input of energySolute passes from area of high concentration to area of lower concentrationb. ACTIVE TRANSPORTa. Requires input of energySolute transported from area of low concentrationto area of higher concentration IV. Clicker question: G = RT ln (c2/c1), Free-energy change in transporting this species from side 1, where it is present at the concentration c1, to side 2, where it has the concentration c2.A. PASSIVE TRANSPORT - Does not require input of energySolute passes from area of high concentration to area of lower concentration1. G for passive transport isa. . >0b. =0c. <0V. Clicker question: G = RT ln (c2/c1), Free-energy change in transporting this species from side 1, where it is present at the concentration c1, to side 2, where it has the concentration c2.A. ACTIVE TRANSPORT - Requires input of energySolute transported from area of low concentrationto area of higher concentration1.G for active transport isa. >0b. =0c. <0VI. Action potential in neurons is created by ion channelsA. Membrane potential (also transmembrane potential or membrane voltage) is the difference in electric potential between the interior and the exterior of a biological cell. With respect to the exterior of the cell, typical values of membrane potential range from –40 mV to –80 mV.VII. Free energy change for transport of substrates across a membrane- membrane potentialA. For a charged molecule, the unequal distribution across the membrane will also generate an electric potential, that must be considered as ions will be repelled by like charges. The sum of concentration and electrical terms is called the electrochemical or membrane potential. The free energy change is then given as: G = RT ln (c2/c1) + ZF VB. Free-energy change in transporting this species from side 1, where it is present at the concentration c1, to side 2, where it has the concentration c2.1. Z is the electrical charge of the cargo.2. V is the potential in Volts across the membrane.3. F is the Faraday constant (96.5 kJ V-1 mol-1). 4. T is the temperature in kelvins . 5. R is the gas constant (8.135 * 10-3 kJ mol-1 deg-1VIII. Clicker question: A neuron is depolarized from its resting potential (-60 mV, more negative in the cell) to its action potential (30 mV, more positive in the cell), by the influx of sodium ions into the cell. Assume that the sodium concentration is equal inside and outside of the cell after depolarization. What is the free energy change in transporting sodium molecules out of the cell?A. G = RT ln (c2/c1) + ZFVB. Free-energy change in transporting this species from side 1, where it is present at the concentration c1, to side 2, where it has the concentration c2. T is the temperature in kelvins and R is the gas constant (8.135 * 10-3 kJ mol-1 deg-1). Z is the electrical charge of the cargo. V is the potential in Volts across the membrane (determined by the ratio of internal to external concentration of ions), and F is the Faraday constant (96.5 kJ V-1 mol-1).1. G for transport isa. >0b. =0c. <0 First term is 0, V is -30mV as Na is transported from inside to outside . IX. Electrical gradient changes the equilibriumX. At equilibrium, membrane potential is given by the Nernst equation:A. Veq= -(RT/zF) * ln(cin/cout)1. z is the electrical charge of the cargo.2. Veq is the potential across the membrane, when the driving force due to the concentration gradient is balanced by the electrostatic force that resists the motion of an additional charge.3. F is the Faraday constant (96.5 kJ V-1 mol-1). 4. T is the temperature in kelvins . 5. R is the gas constant (8.135 * 10-3 kJ mol-1 deg-1).6. cin/cout is the concentration gradient from inside to outside of the cell.XI. Action potential in neurons is created by ion channels XII. Potassium channels and the atomic basis of selective ion conduction (Nobel Lecture).A. MacKinnon R. Angew Chem Int Ed Engl. 43(33):4265-77.XIII. Ion channels – the selectivity filterXIV.Table 13.1XV. Ion channels – the selectivity filterXVI. Ion channels – the selectivity filterXVII. Ion channels – the selectivity filterXVIII. Ion channels – the selectivity filterXIX. Ion channels – the selectivity filterXX. Ion channels – the selectivity filterXXI. Ion channels – the selectivity filterA. Na+ is smaller, why doesn’t it pass through?B. To transport K+, transporter uses its C=O to substitute for the O of water surrounding K+C. Not easy for the Na+ to give up its surrounding water since C=O cannot reachXXII. Ion channels – the selectivity filterA. How do K+ ions move through once bound?XXIII. Ion channels – the selectivity filterXXIV. Ion channels – the selectivity filterXXV. Ion channels – the selectivity filter – repulsion of like chargesA. 4 binding sites for K+B. Repulsion of like charges allow for K+ to move from one