lecture notes

lecture notes - There is nothing in the dark that isn't...

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There is nothing in the dark that isn't there when the lights are on. Rod Serling Outside of a dog, a book is a man's best friend. Inside of a dog it's too dark to read. Groucho Marx The light at the end of the tunnel is the front of an oncoming train. David Lee Roth, “Perfect Timing”
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Announcements The next quiz is due next Wednesday, Oct. 19 at noon. It covers the TCA cycle, electron transport chain, and ATP synthesis (not photosynthesis). Please turn in a hard copy of the research article summary, either in class on Friday or outside of my door by noon this Friday. Also, please turn it in through Blackboard.
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H + gradient formed across inner mito. membrane using energy from electron transport The H + gradient is then used to drive ATP synthesis by ATP synthase The electron transport chain and oxidative phosphorylation do not directly make any ATP
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The proton motive force drives ATP synthesis Translocation of H+ produces two things: a pH gradient and a voltage gradient E H+ = -60 z log10[Hin/Hout] (Nernst equation) CORRECTION: Here [Hin] is for matrix and [Hout] is intermembrane space, which will give the correct sign for p 2200 p is measuring the magnitude of the 2200 p = ∆ ψ – 60 pH is the proton motive force 2200 ψ is the magnitude of the potential difference across the membrane, which is about 180 mV, pH gradient 0.5-1 pH unit For active mitochondria, p ~ +220 mV "+"-charged, lipid-soluble dyes such as rhodamine that distribute themselves across membranes in proportion to electric potential
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Schematic of ATP synthase Head called F1 Membrane embedded portion called F0 Actually two connecting stalks, a central and peripheral one F1 of ATP synthases contain 5 different polypeptides ( α, β, δ, γ , ε ) with the following stoichiometry ( α 3 β 3 δ γ ε ) subunits arranged alternately in F1 head like orange segments Each F1 contains 3 catalytic sites for ATP synthesis (one on each β subunit) F0 portion of ATP synthase consists of 3 different polypeptides with stoichiometry ab2c10-14, where number of c depends on species F0 F1
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Basic hypothesis of ATP formation 7.3 kcal/mole under standard conditions is needed to form ATP, but…. When substrates & product are bound to ATP synthase, G nearly 0 & thus it can occur spontaneously, without energy input Proton motive force only alters affinity of ATP for binding site, but does not contribute to ADP+Pi → ATP itself
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There are three possible states for the catalytic site on each β subunit O (open) conformation – low affinity for nucleotides, ATP is released L (loose) conformation – ADP and Pi loosely bound T (tight) conformation – ATP or ADP and Pi tightly bound At any given time, the catalytic sites for the three β subunits are each in different conformations, such that one is in L, one is in T, and one is in O Each site passes sequentially from L to T to O and then back to L
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lecture notes - There is nothing in the dark that isn't...

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