Essential Elements of Biochemistry BCHM 3050 Dr Srikripa Chandrasekaran Lecture 4 13 15 Notes Respiratory Electron Transport continued I Positioning of Four Complexes in Cristae Membrane A 1 molecules of glucose in the cytoplasm goes through glycolysis and yields 2 ATP net yield and 2 NADH H B Mitochondria outer membrane cristae inner membrane matrix 1 In the matrix is where the TCA cycle happens most of the enzymes are located in the matrix except for succinate dehydrogenase which is in the inner membrane 2 2 pyruvates yield acetyl CoA 2 NADH H this NADH H is generated from glycolysis 3 2 Acetyl CoA goes through the TCA cycle and 6 NADH H and 2 FADH2 are produced 8 NADH H and 2 FADH2 total 4 NADH H is the reduced form 5 NADH H is full of electrons because NAD accepts electrons in order to form NADH H 6 Protons accumulate in the inner membrane space 7 There are 4 compartments in mitochondria and all 4 are rich in proteins opposite direction 8 The red arrow on the green complex should be pointing in the 9 Oxygen in located in the matrix 10 The proteins can accept electrons from NADH and can then pass them on to other proteins 11 Oxygen is the last electron acceptor 12 Oxygen has the highest reduction potential 13 NAD has a lower reduction potential II Four Membrane Complexes Are Involved in Respiratory Electron Transport A Complex 1 converts NADH to NAD so it oxidizes NADH back to NAD NADH can give up the electrons B Complex 2 succinate DH complex located in the inner membrane generates FADH2 FADH2 can now give up its electrons to other proteins C Complex 4 cytochrome c oxidase is an evolutionary mark across species and has been passed on faithfully through evolution D Giving off carbon dioxide happens in the beginning while the taking in III of oxygen occurs at the end oxygen is an electron acceptor Four Complexes of Electron Transport A The entire action happens in the cristae inner membrane B Most of the NADH and FADH2 are present here 1 IV Four Important Biomolecules Involved in Respiratory Electron Transport A The 4 complexes are rich in these proteins B Ubiquinone is the one protein that can move through the membranes and carry electrons C The flavoproteins can accept and give up protons they can do 1 or 2 electron or proton transfers at a time D Non hemoglobin proteins have iron they can do single electron E Cytochromes contain 1 iron atom and they can transfer a single transfers electron highly lipophilic F There are 4 electron transfers that happen within complex 1 G Electrons are being passed from protein to protein H Complex 1 is rich in flavoproteins and ubiquinone comes in and out of complex 1 you will never find cytochrome proteins or copper in complex 1 I Complex 2 is a collector it collects the final electrons from complex 1 and complex 2 and passes them on to complex 3 J Complex 3 no flavoproteins contains only iron sulfur proteins and cytochrome proteins K Complex 4 is the only complex that has copper it also has cytochromes copper is ultimately the one that donates the electrons to oxygen then oxygen gets reduced to water L Cytochrome C can accept electrons from Complex 3 and give them to Complex 4 V M Cytochromes do not receive electrons from FADH2 A Closer Look at Complex I A Complex 1 NADH dehydrogenase contains flavoproteins Fe S proteins and CoQ moves in and out of it B Fats can also enter the electron transport chain at this point C FMN gets reduced to FMNH2 D Ubiquinone gets reduced to UbiquinoneH2 E Accumulate 4 protons in this inner membrane space F When you accept an electron you also accept a proton G You get 4 protons they move from the matrix to the inner membrane space for every NADH that gets oxidized back to NAD H There are no specified transporters for these protons A Closer Look at Complex II A Complex 2 is a succinate dehydrogenase complex B FAD transfers the electrons to ubiquinone C The NADH from glycolysis enters complex 2 A Closer Look at Complex III The Q Cycle A Complex 3 is also called the Q Cycle B Complex 3 has cytochromes and Fe S proteins but not flavoproteins C The electrons come solely from ubiquinone D Electrons trade hands between ubiquinone and Complex 3 E Proteins come in and ubiquinone gets reduced and then reoxidized VI VII 2 F 4 protons per NADH from Complex 3 4 protons from Complex 1 no protons from Complex 2 4 protons from Complex 3 VIII Electron transport Through Complex IV Cytochrome Oxidase A Copper gives electrons to oxygen oxygen takes the electrons to IX X protons and gets reduced to water B Complex 4 is rich in copper and cytochrome proteins C 2 protons from Complex 4 accumulated 10 total protons in the inner membrane space 4 protons from Complex 1 4 protons from Complex 3 2 protons from Complex 4 Electron Transport in Relation to Reduction Potentials A NADH has the lowest reduction potential Some Poisons are Inhibitors of Respiratory Electron Transport A Some poisons are inhibiters B You should not consume rat poison because it acts on eukaryotes C Antimycin blocks electron transfer within Complex 3 D Cyanide prevents electron transfer from copper to oxygen kills you if E Barbituate truth serum inhibits transfer of electrons from Complex consumed 1 to Complex 2 F Rotenone is a fishacide used to kill fish if it is washed out into the sea or rivers the fish die if fish consume it and then humans consume those fish it can have harmful effects on humans 3
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