Lecture 11: Citric Acid Cycle, ETC and Fermentation Flashcards
Where does pyruvate oxidation occur?
Mitochondria
What is pyruvate oxidation coupled with?
The reduction of NAD+ to NADH
The half-reactions produce a lot of energy, what is this energy used for?
To generate a covalent bond to coenzyme A
What is the final product of pyruvate oxidation?
2 molecules of acetyl coenzyme A
Where do the acetyl coenzyme A’s go after pyruvate oxidation?
Citric Acid Cycle
Where does the citric acid cycle occur?
Mitochondria
What does dehydrogenase do?
Catalyzes redox reactions
What are the products of the citric acid cycle?
- 3 NADH
- 1 FADH2
- 1 GTP = 1 ATP
Why does one step reduce FAD instead of NAD+ ?
-FAD has a higher redox potential meaning that the electrons are more likely to flow there away from NAD+
-If FAD was not there the cycle would go in the opposite direction and would be useless
What is the main function of the ETC?
Converts NADH and FADH2 molecules back to NAD+
- Shuttles electrons to oxygen
Where does the ETC occur?
In the Christae of the mitochondria
How does complex I work?
- NADH binds to the first complex and gives up its two electrons
- There is a cofactor bound to the enzyme that gets reduced. This reaction releases enough energy to cause a conformational change of complex I.
- The energy results in the transport of a proton across the inner mitochondrial membrane against the concentration gradient.
What does ubiquinone do in the ETC?
-The electron from the oxidation of NADH is transferred via ubiquinone to complex III.
-Ubiquinone gets reduced by taking up the electron and a proton at the same time.
Why can ubiquinone pass laterally through the plasma membrane?
-Ubiquinone is hydrophobic
True or False: There are binding sites for ubiquinone outside of complex I and complex III
False , there is one outside of complex I but the one for complex III is on the inside
How does complex III work?
Ubiquinone binds to complex III then it gets oxidized and the proton goes across the concentration gradient again through complex III and the electron is passed on.
Why does FADH2 need to be oxidized at a unique protein complex?
FADH2 carries less energy than NADH which is why it must be oxidized at it unique protein complex, complex II.
-Cannot use complex I because it transfers one less proton across the gradient.
How does complex II work?
-Electrons enter complex II via oxidation of FADH2.
-Electrons are then used to reduce ubiquinone and are then transferred to complex III
Does complex II have a protein pump?
No
What is cytochrome C?
Hydrophobic protein found between complexes III and IV
What does cytochrome C do?
Transports electrons from complex III to complex IV
How does complex IV work? (not including oxygen part)
-Complex IV is reduced by cytochrome C resulting in a conformational change leading to a release of energy and protons being transported across the membrane
How does complex IV work? (including oxygen)
-A cofactor and heme group hold an oxygen molecule tight, in position for complex IV to reduce it with electrons
-The O2 is then reduced to produce H2O
What are heme groups?
Iron or copper atoms
How does cyanide cause death?
Cyanide can bind irreversibly(covalently) to a heme group preventing oxygen from being reduced which leads to death by suffocation
What is the electrochemical proton gradient?
Gradient that is electric(charge difference), chemical gradient(more protons one side than the other), there is a pH difference and voltage difference they generate what is called an electromotive force.
