Oxidative Phosphorylation Flashcards
What are cytochromes?
Iron coordinating porphyrin ring derivatives
One electron carriers
What are Iron sulfer clusters?
Iron and sulfer atoms coordinated by cysteine residues
What is Ubiquinone?
Small, mobile carrier that transfers electrons between the primary dehydrogenases and cytochrome b
Reduced form donates its electrons to Complex III
What is Rieske irone sulfur protein?
Non-heme-iron protein component of complex III
How are electrons transferred through complex I?
NADH transfers two electrons to ubiquinone
How many protons are transported through complex I?
4
What is complex II and how are electrons transported through it?
Succinate dehydrogenase
FAD accepts two electrons from succinate, which are eventually transferred to ubiquinone via iron-sulfur centers
What is complex III and how are electrons transferred through it?
Ubiquinone: Cytochrome c oxidoreductase
Uses two electrons from QH2 to reduce two molecules of cytochrome c
What is Cytochrome c?
Mobile electron carrier that moves through the intermembrane space
Carries electron from the cytochrome bc1 complex to cytochrome oxidase
What is the Q cycle?
The process by which electrons a recycled in complex III via a semiquinone radical
How does the Q cycle contribute to the proton gradient?
When semiquinone accepts its second electron, it extracts two more protons from the matrix in addition to the four that have been pumped out via the two electrons that were transferred to cytochrome c
What is complex IV and how are electrons transferred through it?
Cytochrome c donates its electrons to CuA–>CuB
CuB transfers FOUR electrons to ONE oxygen molecule
How many protons are transferred through complex IV per oxygen?
4
What is the function of the Malate-Aspartate shuttle and where does it take place?
Moves NADH from the cytosol to the the matrix
Liver, kindey and heart
Generates more ATP than glycerol-3-phosphate shuttle
What is the role of the glycerol-3-phosphate shuttle and where does it take place?
Moves NADH from cytosol to inner mitochondrial space
Skeletal muscle and brain
Donates electrons to FADH2, skipping complex I, and therefore generating less of a proton gradient
Why is the proton-motive force an electrochemical gradient?
Chemical difference - pH gradient generated by H+
Electrical difference - Charge difference generated from H+
What is the function of amytal and rotenone?
Complex I inhibitor
What is the role of antimycin A?
Complex III inhibitor
What is the function of cyanide, CO, hydrogen sulfide, and sodium azide?
Complex IV inhibitor
What is the function of oligomycin?
Complex V or ATP synthase inhibitor
What are the two functional units of ATP synthase?
F1 - soluble part of the complex exposed to matrix, catalyzes formation of ATP
Fo - integral part, transports protons to matrix
How is ADP and phosphate stabilized in ATP synthase?
Positively charged amino acids
Describe the binding-change model for ATP synthase?
Proton translocation causes rotation and conformational change within all three aB pairs in Fi
Conformational changes between open, loose, and tight causes the formation of ATP
What is the function of IF1?
Inhibits ATPase activity by binding to two ATP synthase molecules
Only active at low oxygen and low pH
What is the function of adenine nucleotide translocase?
Antiporter that exchanges ADP for ATP across the inner membrane
Uses up membrane potential - one charge per ATP
What is the function of Phosphate translocase?
Symporter that moves Phosphate and H+ into the matrix
Uses up pH gradient - one mol H+ per mol ATP
How many H+ are needed per ATP molecule generated and why?
3 H to synthesize one ATP through ATP synthase
1 H to transport P- into the matrix
How many ATP are generated per NADH?
2.5
How many ATP are generated per FADH2?
1.5
