Final: Chapter 11 Oxidative Phosphorylation Flashcards
What is the chemiosmotic theory?
Theory proposed by Peter Mitchell that describes energy conversion in essentially all organisms
Where in the cell is does the chemiosmotic theory take place?
The mitochondria
How is the proton gradient in the chemiosmotic theory established across the mitochondrial inner membrane?
With chemiosmosis (the movement of protons down a concentration gradient). The gradients moves from high concentrations of protons to low concentrations.
ALSO ATP is produced :)
What initiates a proton gradient?
Outward pumping of H+ from the mitochondrial matrix by three large protein complexes
What does inward flow of H+ through the membrane bound ATP synthase protein accomplish?
ATP synthesis
What is the electron transport chain ?
The combined redox reactions that occur in a set of protein complexes embedded in the inner mitochondrial membranes. NADH is oxidized to form NAD+ and O2 (the final electron acceptor) is reduced to H2O
The proton circuit behaves like an electrical circuit. What molecules act as the resistor, capacitor, and battery?
ATP synthase is the resistor, the proton gradient is the capacitor, and the battery is the electron transport system
How does proton uncoupling stop ATP synthesis?
Proton uncoupling is when a fraction of the proton gradient generated by the electron transport chain is not used to drive ATP synthesis. It causes a proton “leakage” and produces heat
What are the main structural features of the mitochondria?
Outer mitochondrial membrane, intermembrane space, inner mitochondrial membrane, cristae (folds within the inner mitochondrial membrane), and the mitochondrial matrix
Referring to protein components of the electron transport chain: What protein is in Complex I?
NADH-ubiquinone oxidoreductase
Referring to protein components of the electron transport chain: What protein is in Complex II?
Succinate dehydrogenase
Referring to protein components of the electron transport chain: What protein is in Complex III?
Ubiquinone-cytochrome c oxidoreductase
Referring to protein components of the electron transport chain: What protein is in Complex IV?
Cytochrome oxidase
Referring to protein components of the electron transport chain: What protein is in Complex V?
ATP synthase complex
Which complexes in the electron transport system contain transmembrane regions that are embedded in the inner mitochondrial membrane as well as functional domains that face toward the mitochondrial matrix?
Complexes I - IV
In which complex does NADH oxidation occur?
Complex I which can pump four hydrogen ions across the membrane from the matrix into the intermembrane space, thereby establishing a proton gradient
Where does the ETC take place?
On the matrix side of the inner mitochondrial membrane
What are the main inhibitors of the ETC?
Rotenone, hydrogen cyanide, carbon monoxide, and antimycin A
What are redox loops?
A type of arrangement where protons and electrons are separated on opposite sides of the membrane.
Which complex is a redox loop?
Complex III (Q cycle)
Proton pumps for the ETC are dependent on what?
The conformational changes of Complexes I and IV
What happens in Complex I and what important protein is involved?
- This complex includes flavin mononucleotide (FMN) and NADH-ubiquinone oxidoreductase
- NADH is oxidized while Coenzyme Q is reduced
- FMN accepts 2 electrons from NADH
How is semiquinone and reduced flavin mononucleotide formed from flavin mononucleotides?
Flavin mononucleotides are reduced one electron at a time
What does Coenzyme Q do?
Acts as mobile electron carrier and transports electrons from Complex I to Complex III
Coenzyme Q’s activity serves as an entry point for what other molecules/pathways?
Citrate cycle, fatty acid oxidation, and glycerol-3-phosphate dehydrogenase
What happens when Coenzyme Q is reduced?
Ubiquinol (QH2) forms and 4H+ are translocated from the matrix side of the membrane to the intermembrane space
What happens in Complex II and what important protein is involved?
- With succinate dehydrogenase, this complex catalyzes the oxidation-reduction reaction of succinate to fumarate.
- Coupled redox reaction using FAD and reduction of coenzyme Q to QH2
What happens in Complex III and what important protein is involved?
- With Ubiquinone-cytochrome C oxidoreductase, cytochrome C is reduced while translocating 4H+
- This complex is a docking site for QH2 and cytochrome c
What does the Q cycle convert?
Converts a 2 electron transport process into two 1 electron transfers
Where do electrons come from in the Q cycle?
Coenzyme Q
Where does Q cycle occur and what happens during it?
Occurs in Complex III. Cytochrome c is reduced and transports 1 electron from Complex III to Complex IV
What are cytochrome proteins?
Membrane associated, heme-containing proteins involved in electron transport-redox reactions
What happens in Complex IV and what important protein involved?
Cytochrome c oxidase accepts electrons one at a time. While cytochrome c is oxidized, oxygen is reduced to water. ALSO, 2H+ are translocated across the membrane
What two large structural components comprise the ATP synthase complex?
F1 (encodes catalytic activity) and F0 (acts as a proton channel crossing the inner mitochondrial membrane)
Where do protein flow through in ATP synthase and what happens?
They flow through the F0 component which induces the F1 subunit to undergo a conformation change (loose to tight and then open). ATP is released only in the open position
What two shuttles are used to shuttle biomolecules required for the ETC and oxidative phosphorylation?
Malate-aspartate shuttle (liver) and glycerol-3-phosphate (muscle) which transport electrons from cystolic NADH to the mitochondria
How is the import of ADP and P into the mitochondrial matrix accomplished?
By using two translocase proteins located in the inner mitrochondrial matrix: ATP/ADP translocase (exports one ATP for every ADP imported) and phosphate translocase (translocates one P and one H+ into the matrix)
What is ATP-ADP translocase?
An antiporter membrane transport protein
What is phosphate translocase?
Protein similar to a channel that can act as a symporter (two molecules moved in the same direction) or antiporter (two molecules moved in opposite directions). It is also electrically neutral
What is the malate-aspartate shuttle and what’s important about it?
It is the primary shuttle in liver cells whose reactions are all reversible. It maintains the supply of NAD+
What is the glycerol-3-phosphate shuttle and what’s important about it?
Shuttle that consists of two isozymes of glycerol-3-phosphate dehydrogenase. It delivers electrons from NADH to the mitochondrial matrix using FAD. Electrons from NADH got into the ETC through coenzyme Q
