chapter 14 - electron transport and oxidative phosphorylation the cheetah, whose capacity for...
TRANSCRIPT
![Page 1: Chapter 14 - Electron Transport and Oxidative Phosphorylation The cheetah, whose capacity for aerobic metabolism makes it one of the fastest animals](https://reader035.vdocuments.mx/reader035/viewer/2022062421/56649cac5503460f9496ee5d/html5/thumbnails/1.jpg)
Chapter 14 - Electron Transport and Oxidative Phosphorylation
• The cheetah, whose capacity for aerobic metabolism makes it one of the fastest animals
![Page 2: Chapter 14 - Electron Transport and Oxidative Phosphorylation The cheetah, whose capacity for aerobic metabolism makes it one of the fastest animals](https://reader035.vdocuments.mx/reader035/viewer/2022062421/56649cac5503460f9496ee5d/html5/thumbnails/2.jpg)
Oxidative Phosphorylation in Mitochondria
• Oxidative phosphorylation is the process by which NADH and FADH2 are oxidized and ATP is formed
• NADH and FADH2 are reduced coenzymes from the oxidation of glucose by glycolysis and the citric acid cycle
The Respiratory Electron-transport Chain (ETC) is a series of enzyme complexes embedded in the inner mitochondrial membrane, which oxidize NADH and QH2. Oxidation energy is used to transport protons across the inner mitochondrial membrane, creating a proton gradient
ATP synthase is an enzyme that uses the proton gradient energy to produce ATP
![Page 3: Chapter 14 - Electron Transport and Oxidative Phosphorylation The cheetah, whose capacity for aerobic metabolism makes it one of the fastest animals](https://reader035.vdocuments.mx/reader035/viewer/2022062421/56649cac5503460f9496ee5d/html5/thumbnails/3.jpg)
Mitochondria are energy centers of a cell
MitochondriaCytosol
![Page 4: Chapter 14 - Electron Transport and Oxidative Phosphorylation The cheetah, whose capacity for aerobic metabolism makes it one of the fastest animals](https://reader035.vdocuments.mx/reader035/viewer/2022062421/56649cac5503460f9496ee5d/html5/thumbnails/4.jpg)
Fig 14.2
![Page 5: Chapter 14 - Electron Transport and Oxidative Phosphorylation The cheetah, whose capacity for aerobic metabolism makes it one of the fastest animals](https://reader035.vdocuments.mx/reader035/viewer/2022062421/56649cac5503460f9496ee5d/html5/thumbnails/5.jpg)
• Final stages of aerobic oxidation of biomolecules in eukaryotes occur in the mitochondrion
• Site of citric acid cycle and fatty acid oxidation which generate reduced coenzymes
• Contains electron transport chain to oxidize reduced coenzymes
Fig 14.6Structure of the
mitochondrion
![Page 6: Chapter 14 - Electron Transport and Oxidative Phosphorylation The cheetah, whose capacity for aerobic metabolism makes it one of the fastest animals](https://reader035.vdocuments.mx/reader035/viewer/2022062421/56649cac5503460f9496ee5d/html5/thumbnails/6.jpg)
Overview of oxidative phosphorylation
Fig 14.1
![Page 7: Chapter 14 - Electron Transport and Oxidative Phosphorylation The cheetah, whose capacity for aerobic metabolism makes it one of the fastest animals](https://reader035.vdocuments.mx/reader035/viewer/2022062421/56649cac5503460f9496ee5d/html5/thumbnails/7.jpg)
Electron Flow in Oxidative Phosphorylation
• Five oligomeric assemblies of proteins associated with oxidative phosphorylation are found in the inner mitochondrial membrane
• Complexes I-IV contain multiple cofactors, and are involved in electron transport
• Electrons flow through complexes I-IV
• Complexes I, III and IV pump protons across the inner mitochondrial membrane as electrons are transferred
• Mobile coenzymes: ubiquinone (Q) and cytochrome c serve as links between electron transport complexes
• Complex IV reduces O2 to water
• Complex V is ATP synthase, which uses the generated proton gradient across the membrane to make ATP
![Page 8: Chapter 14 - Electron Transport and Oxidative Phosphorylation The cheetah, whose capacity for aerobic metabolism makes it one of the fastest animals](https://reader035.vdocuments.mx/reader035/viewer/2022062421/56649cac5503460f9496ee5d/html5/thumbnails/8.jpg)
![Page 9: Chapter 14 - Electron Transport and Oxidative Phosphorylation The cheetah, whose capacity for aerobic metabolism makes it one of the fastest animals](https://reader035.vdocuments.mx/reader035/viewer/2022062421/56649cac5503460f9496ee5d/html5/thumbnails/9.jpg)
![Page 10: Chapter 14 - Electron Transport and Oxidative Phosphorylation The cheetah, whose capacity for aerobic metabolism makes it one of the fastest animals](https://reader035.vdocuments.mx/reader035/viewer/2022062421/56649cac5503460f9496ee5d/html5/thumbnails/10.jpg)
Cofactors in Electron Transport
• NADH donates electrons two at a time to complex I of the electron transport chain
• Flavin coenzymes are then reduced
(Complex I) FMN FMNH2
(Complex II) FAD FADH2
• FMNH2 and FADH2 donate one electron at a time to ubiquinone (U or coenzyme Q)
• All subsequent steps in electron transport proceed by one electron transfers
![Page 11: Chapter 14 - Electron Transport and Oxidative Phosphorylation The cheetah, whose capacity for aerobic metabolism makes it one of the fastest animals](https://reader035.vdocuments.mx/reader035/viewer/2022062421/56649cac5503460f9496ee5d/html5/thumbnails/11.jpg)
Mobile electron carriers
1. Ubiquinone (Q)Q is a lipid soluble molecule that diffuses within the lipid bilayer, accepting electrons from Complex I and Complex II and passing them to Complex III.
2. Cytochrome cAssociated with the outer face of the inner mitochondrial membrane. Transports electrons from Complex III to Complex IV.
![Page 12: Chapter 14 - Electron Transport and Oxidative Phosphorylation The cheetah, whose capacity for aerobic metabolism makes it one of the fastest animals](https://reader035.vdocuments.mx/reader035/viewer/2022062421/56649cac5503460f9496ee5d/html5/thumbnails/12.jpg)
Iron in metalloenzymes
• Iron undergoes reversible oxidation and reduction:
Fe3+ + e- (reduced substrate)
Fe2+ + (oxidized substrate)
• Enzyme heme groups and cytochromes contain iron
• Nonheme iron exists in iron-sulfur clusters (iron is bound by sulfide ions and S- groups from cysteines)
• Iron-sulfur clusters can accept only one e- in a reaction
![Page 13: Chapter 14 - Electron Transport and Oxidative Phosphorylation The cheetah, whose capacity for aerobic metabolism makes it one of the fastest animals](https://reader035.vdocuments.mx/reader035/viewer/2022062421/56649cac5503460f9496ee5d/html5/thumbnails/13.jpg)
Iron-sulfur clusters
• Iron atoms are complexed with an equal number of sulfide ions (S2-) and with thiolate groups of Cys side chains
Heme Fe(II)-protoporphyrin IX
• Heme consists of a tetrapyrrole Porphyrin ring system complexed with iron
![Page 14: Chapter 14 - Electron Transport and Oxidative Phosphorylation The cheetah, whose capacity for aerobic metabolism makes it one of the fastest animals](https://reader035.vdocuments.mx/reader035/viewer/2022062421/56649cac5503460f9496ee5d/html5/thumbnails/14.jpg)
Complex I. NADH-ubiquinone oxidoreductase
• Transfers two electrons from NADH as a hydride ion (H:-) to flavin mononucleotide (FMN), to iron-sulfur complexes, to ubiquinone (Q), making QH2
• About 4 protons (H+) are translocated across the inner mitochondrial membrane per 2 electrons transferred
Fig 14.9
![Page 15: Chapter 14 - Electron Transport and Oxidative Phosphorylation The cheetah, whose capacity for aerobic metabolism makes it one of the fastest animals](https://reader035.vdocuments.mx/reader035/viewer/2022062421/56649cac5503460f9496ee5d/html5/thumbnails/15.jpg)
Complex II. Succinate-ubiquinone oxidoreductase
• Also known as succinate dehydrogenase complex
• Transfers electrons from succinate to flavin adenine dinucleotide (FAD) as a hydride ion (H:-), to an iron-sulfur complex, to ubiquinone (Q), making QH2
• Complex II does not pump protons
Fig 14.11
![Page 16: Chapter 14 - Electron Transport and Oxidative Phosphorylation The cheetah, whose capacity for aerobic metabolism makes it one of the fastest animals](https://reader035.vdocuments.mx/reader035/viewer/2022062421/56649cac5503460f9496ee5d/html5/thumbnails/16.jpg)
Complex III. Ubiquinol-cytochrome c oxidoreductase
• Transfers electrons from QH2 to cytochrome c, mediated by iron-sulfur and other cytochromes
• Electron transfer from QH2 is accompanied by the translocation of 4 H+ across the inner mitochondrial membrane
Fig 14.14
![Page 17: Chapter 14 - Electron Transport and Oxidative Phosphorylation The cheetah, whose capacity for aerobic metabolism makes it one of the fastest animals](https://reader035.vdocuments.mx/reader035/viewer/2022062421/56649cac5503460f9496ee5d/html5/thumbnails/17.jpg)
Complex IV. Cytochrome c oxidase
• Uses four-electrons from the soluble electron carrier cytochrome c to reduce oxygen (O2) to water (H2O)
• Uses Iron atoms (hemes of cytochrome a) and copper atoms
• Pumps two protons (H+) across the inner mitochondrial membrane per pair of electrons, or four H+ for each O2 reduced
O2 + 4 e- + 4H+ 2 H2O
Fig 14.19
![Page 18: Chapter 14 - Electron Transport and Oxidative Phosphorylation The cheetah, whose capacity for aerobic metabolism makes it one of the fastest animals](https://reader035.vdocuments.mx/reader035/viewer/2022062421/56649cac5503460f9496ee5d/html5/thumbnails/18.jpg)
Complex V: ATP Synthase• F0F1 ATP Synthase uses the proton gradient energy for the
synthesis of ATP
• Composed of a “knob-and-stalk” structure
• F1 (knob) contains the catalytic subunits
• F0 (stalk) has a proton channel which spans the membrane.
• Estimated passage of 3 protons (H+) per ATP synthesized
![Page 19: Chapter 14 - Electron Transport and Oxidative Phosphorylation The cheetah, whose capacity for aerobic metabolism makes it one of the fastest animals](https://reader035.vdocuments.mx/reader035/viewer/2022062421/56649cac5503460f9496ee5d/html5/thumbnails/19.jpg)
Prentice Hall c2002 Chapter 14 19
Knob-and-stalk structure of ATP synthase
![Page 20: Chapter 14 - Electron Transport and Oxidative Phosphorylation The cheetah, whose capacity for aerobic metabolism makes it one of the fastest animals](https://reader035.vdocuments.mx/reader035/viewer/2022062421/56649cac5503460f9496ee5d/html5/thumbnails/20.jpg)
Prentice Hall c2002 Chapter 14 20
Mechanism of ATP Synthase
• There are 3 active sites, one in each subunit
• Passage of protons through the Fo channel causes the c- unit to rotate inside the 33 hexamer, opening and closing the -subunits, which make ATP
![Page 21: Chapter 14 - Electron Transport and Oxidative Phosphorylation The cheetah, whose capacity for aerobic metabolism makes it one of the fastest animals](https://reader035.vdocuments.mx/reader035/viewer/2022062421/56649cac5503460f9496ee5d/html5/thumbnails/21.jpg)
Fig 14.20 Transport of ATP, ADP and Pi across the inner mitochondrial membrane
• Adenine nucleotide translocase: unidirectional exchange of ATP for ADP (antiport)
• Symport of Pi and H+ is electroneutral
![Page 22: Chapter 14 - Electron Transport and Oxidative Phosphorylation The cheetah, whose capacity for aerobic metabolism makes it one of the fastest animals](https://reader035.vdocuments.mx/reader035/viewer/2022062421/56649cac5503460f9496ee5d/html5/thumbnails/22.jpg)
The P:O Ratio
molecules of ADP phosphorylated P:O ratio = -----------------------------------------
atoms of oxygen reduced
• Translocation of 3H+ required by ATP synthase for each ATP produced
• 1 H+ needed for transport of Pi, ADP and ATP
• Net: 4 H+ transported for each ATP synthesized
![Page 23: Chapter 14 - Electron Transport and Oxidative Phosphorylation The cheetah, whose capacity for aerobic metabolism makes it one of the fastest animals](https://reader035.vdocuments.mx/reader035/viewer/2022062421/56649cac5503460f9496ee5d/html5/thumbnails/23.jpg)
Calculation of the P:O ratio
#H+ translocated/2e- 4 4 2
Since 4 H+ are required for each ATP synthesized:
Complex I III IV
For NADH: 10 H+ translocated / O (2e-)
P/O = (10 H+/ 4 H+) = 2.5 ATP/O
For succinate (FADH2) substrate = 6 H+/ O (2e-)
P/O = (6 H+/ 4 H+) = 1.5 ATP/O
![Page 24: Chapter 14 - Electron Transport and Oxidative Phosphorylation The cheetah, whose capacity for aerobic metabolism makes it one of the fastest animals](https://reader035.vdocuments.mx/reader035/viewer/2022062421/56649cac5503460f9496ee5d/html5/thumbnails/24.jpg)
Regulation of Oxidative Phosphorylation
• Overall rate of oxidative phosphorylation depends upon substrate availability and cellular energy demand
• Important substrates: NADH, O2, ADP
• In eukaryotes intramitochondrial ratio ATP/ADP is a secondary control mechanism
• High ratio inhibits oxidative phosphorylation as ATP binds to a subunit of Complex IV