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Chapter 6 total excluding section on cellular respiration .docx

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Matthew Smith

Chapter 6 Reactions of pyruvate oxidation pyruvate + CoA + NAD → acetyl-CoA + NADH + H + CO + 2  transport protein to transport pyruvate  there are two membranes that envelope the mitochondria o contains two membranes  it can easily pass through the first membrane  IT cannot get across the inner membrane with the protein  Consumes ATP  Less then ten years ago they found this protein  Catalyzed by pyruvate dehydrogenase o Removes the carboxyl group which yields carbon dioxide Citric Acid Cycle  Acetyl groups completely oxidized to CO 2  Electrons removed in oxidations + o Accepted by NAD or FAD  Substrate-level phosphorylation  Produces ATP  Each acetyl group oxidized produces o 2 CO 2 o 1 ATP o 3 NADH o 1 FADH 2  In this process, CoA is available to go back and participate in pyruvate oxidation and participate in the cycle again, it is not recycled as part of the citric acid cycle, it is the carbon backbone. It takes the 2 carbons from acetyl-CoA and attaches them to oxaloacetate  One turn of the citric acid cycle:  1 acetyl-CoA + 3 NAD + 1 FAD + 1 ADP + 1 Pi + 2 H O →
 2 CO + 3 NADH + + 2 2 1 FADH 
 2 1 ATP + 3 H + 1 CoA Respiratory Electron Transport Chain  Electrons passed from NADH and FADH2 to O2  Electron Transport Chain includes: o 4 protein complexes o 2 smaller mobile carriers – ubiquinone (UQ) and cytochrome c (cyt c)  Electrons pass through carriers stepwise  Energy released used to pump protons (H+) across inner mitochondrial membrane  3 Major protein complexes (I,III, and IV) o pump H+ o Contain prosthetic groups – redox active cofactors o Cycle between reduced and oxidized states  Electrons o Depleted of energy o Delivered to oxygen as final electron acceptor  Complex I contains 40 separate proteins to form the complex  Complex II is much smaller (1 protein) succinate dehydrogenase (function in both pathways with separate entry points) o Represents the other entry place for electrons into the electron transport chain. Redox Components of the ETC  Prosthetic groups o FMN o Fe-S o Cytochrome (heme)  Electron flow is “downhill” o Each carrier more electronegative than preceding o Electrons will spontaneously flow through the chain o This transfer of electrons is not only spontaneous, but it does NOT produce ATP o Energy is released as it moves through the chain, this energy is used to do work  Such as moving the protons from one side of the membrane to the other in order to generate a concentration gradient  This movement causes a change in pH, the inner membrane space is more acidic then the matrix Oxidative Phosphorylation and Chemiosmosis  ATP synthase catalyzes ATP synthesis using energy from the H+ gradient across the membrane (chemiosmosis) o Proton motive force and the chemiosmotic theory were proposed by Peter Mitchell in 1961, awarded the Nobel prize for this discovery (see page 126- 127).  ATP synthase o Embedded in inner mitochondrial membrane with electron transfer system ATP Synthase – A Molecular Motor  Basal unit embedded in inner mitochondrial membrane o Forms channel for H+ o H+ moves down conc. Gradient into matrix o H+ binds to a site within basal unit causing it to rotate  Basal unit connects to a headpiece by a stalk  Spinning of basal unit and stalk causes ATP formation on the headpiece Uncoupling of Electron Transport and ATP synthesis  Inside the grey box is the matrix  The e- is the input of electrons from NADH  We say then that ATP synthesis is coupled to the electron transport chain. o ATP synthesis would not happen without the ETC  A family of proteins called uncoupling proteins – in humans the
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