Week 7: ETC Flashcards
What are the 4 compartments of the mitochondria?
- Outer membrane
- IMS
- Inner membrane
- Matrix
What is the purpose for the outer membrane of the mitochondria?
- Relatively porous membrane that allow passage of metabolites
- It also allow movement for phosphate, CAC components, ADP and ATP
What is the purpose for the intermembrane space (IMS) of the mitochondria?
Similar environment to cytsol that has a higher proton concentration
What is the purpose for the inner membrane of the mitochondria?
- Impermeable to ions and polar molecules
- Location of the ETC and ATP synthase complexes
- Contains transporters for specific compounds
- Contains cristae
What is the purpose for the matrix of the mitochondria?
- Location of the CAC and parts of lipid and amino acid metabolism
- Has a lower proton concentration
In what ways is the ETC considered a serious of coupled redox reactions?
- Electrons flow from NADH to O2 by large protein complexes
- Acts as a bucket brigade for e- carriers
- Facilitate rapid transfer of substrate while preventing intermediates from forming
- FADH2 electrons feed in after NADH it has lower reduction potential
- Fe is a prosthetic group for each protein in the ETC
Where do the electrons for the ETC come from?
Matrix side of mitochondria
Can reduced coenzymes cross the inner mitochondrial membrane?
No it needs a shuttle
What are the two methods of feeding electrons from NADH in cytosol into the mitochondria?
- Malate-aspartate shuttle
2. Glycerol-3-phosphate shuttle
What is the purpose of Coenzyme Q?
Lipophillic shuttle that carries electrons and H+ from the inside of the mitochondria to the IMS
Which complex is also a part of the CAC?
Complex II
How many electrons are transferred from NADH to coenzyme Q?
2
What occurs during Complex I?
- NADH-Ubiquinone Oxidoreductase
- NADH → FMN → Fe-S → Coenzyme Q
- Coenzyme Q is reduced to QH2
- 4H+ is released from matrix to IMS
What occurs during Complex II?
- Succinate dehydrogenase also a part of CAC
- Succinate transfers 2e- to FAD → SD reduces FAD to FADH2 → FADH transfer 2e- to Fe-S → Fe-S trnasfers 2e- to Coenzyme Q
- Coenzyme Q reduced to QH2
- Reduction of FAD to FADH2
- Oxidizes succinate to fumerate
What occurs during Complex III?
- Coenzyme Q transfers electrons to III
- Complex III contains 2 cytochrome c (can accept electrons) and transfers 2 electrons
- Cytochrome c shuttles e- to Complex IV?
- 4H+ are transferred to IMS
What occurs during Complex IV?
- Catalyzes the formation of water from e-, H+, and O2
- Every 2e- that are transferred, 2H+ are translocated to IMS
- O2 reacts with 2H+ from matrix to form water
- Protons transferred across membrane create pH gradient
How is a proton gradient generated for ATP synthesis?
The ETC uses energy released from electrons to pump H+ to the IMS
What are the pathways that comprised cellular respiration?
CAC and oxidative phosphorylation
What is cellular respiration?
An ATP generating process where O2 serves as an electron acceptor
Where would the electrons of the ETC flow?
4 protein complexes embedded in the IMM
What coenzymes donate electrons to O2 during ETC?
NADH and FADH2 are oxidized reducing O2 to H2O
Is the reduction of O2 exergonic or endergonic?
Exergonic
Why is NADH considered a strong reducing agent?
- Ready to donate electrons
2. Negative reduction potential
Why is O2 considered a strong oxidizing agent?
- Ready to accept electrons
2. Positive reduction potential
How many protons are used for ATP synthase?
4H+
How much ATP does FADH2 make?
1.5ATP
How much ATP does NADH make?
2.5ATP
What is the difference between synthase and synthetase?
Synthetase uses ATP, synthase can make ATP
What is the importance of mitochandrial structure in regards to ATP production?
- E- pass through Complexes I, III, and IV leading to the pumping of protons from IMM to matrix to IMS creating a pH gradient
- The difference between the H+ concentration in matrix and IMS is the basis of coupling between oxidation and phosphorylation
- The proton gradient is the source of energy to drive ATP synthase
What occurs during Complex V?
- 4 Protons go down its gradient to drive ATP synthase
- Phosphate joins ADP to make ATP
- ATP is synthesized in the mitochondria then translocated to the cytoplasm by a cotransporter that simultaneously brings ADP into the mitochondria
How do we make ATP with the reaction is thermodynamically unfavorable?
- Reduced substrate donates e-
- ELectron carriers pump H+ out as e- flow to O2
- Energy of e- flow stored as electrochemical potential
- ATP synthase uses electrochemical potential to synthesize ATP
How is ADP and Pi translocated to the matix?
Translocase proteins located in the inner mitochandrial matrix
What are the 2 translocase proteins that translocate ADP and Pi?
- Adenine nucleotide translocase: the export ATP for every ADP imported
- Phosphate translocase: translocates on Pi and 1H+ into the matix
What occurs when oxidative phosphorylation lacks O2?
No ATP is genreated
What are the three factors that reguate oxidative phosphorylation based on its availabilty?
- NADH
- ATP
- ADP/Pi
How does high NADH effect the oxidative phosphorylation?
High NADH/NAD+ ratio inhibits dehydrogenase reaction of CAC (high energy state)
How does high ATP effect the oxidative phosphorylation?
Increased ATP inhibits glycolysis and CAC (high energy state)
How does high ADP/Pi effect the oxidative phosphorylation?
Activates glycolysis, CAC and respiratory chain (low energy state)
How does high NADH inhibit oxidative phosphorylation?
Causes feedback inhibition cascade up to pyruvate kinase in glycolys
What causes the formation of ROS during oxidative phosphorylation?
Coenzyme Q is naturally leaky and facilitates partial reduction of Complex III targets where single e- transfers result in free radicals
What are the overall reactions that convert free radicals to H2O?
- Superoxide dismutase converts free radical to H2O2
- NADPH from PPP reduces glutathion eliminating toxic free radicals
- H2O2 is converted to H2O by glutathione peroxidase
What type of force is used to drive the sythesis of ATP in OP?
Electrochemical proton-motive force
