8 Oxidative Phosphorylation Flashcards
Acetyl CoA is produced from:
Multiple different catabolic processes
- amino acids, monosaccharides and fatty acids all yield Acetyl CoA as a common molecule
Acetyl CoA enters into the _______ cycle and generates a lot of _________
In other words, the oxidation of the carbons in Acetyl CoA is associated with the reduction of _______ to _______
Acetyl CoA enters into the citric acid cycle and generates a lot of reduced cofactors (NADH/FADH2)
In other words, the oxidation of the carbons in Acetyl CoA is associated with the reduction of NAD+/FAD to NADH/FADH2
The high energy molecules (reduced cofactors NADH/FADH2) produced from the citric acid cycle can be oxidized back to NAD+/FAD via _________ and in the process, it leads to the reduction of ___ to generate H2O and leads to the formation of ______
The high energy molecules (reduced cofactors NADH/FADH2) produced from the citric acid cycle can be oxidized back to NAD+/FAD via Oxidative phosphorylation and in the process, it leads to the reduction of Oxygen to generate H2O and leads to the formation of ATP
- Requires oxygen
What are the two purposes of Catabolic pathways?
- Breakdown of larger molecules into smaller building units
- Release and (temporary) storage of energy in high-energy molecules
- ATP/NTPs
- Reduced cofactors (NADH/FADH2)
Catabolic pathways are ______ (oxidative or reductive)
Catabolic pathways are Oxidative (oxidative or reductive)
- Metabolites are oxidized as cofactors are reduced
- Re-oxidation of cofactors is used to generate ATP (source of e- to drive e- transfer processes to make more ATP through Oxidative phosphorylation)
How are Reduced cofactors used in oxidative phosphorylation?
Re-oxidation of cofactors is used to generate ATP (source of electrons to drive e- transfer processes to make more ATP through Oxidative phosphorylation)
What are the two “separate but connected” processes of Oxidative Phosphorylation?
What links the two processes?
-
Oxidation of reduced cofactors (NADH, FADH2)
- NADH → NAD+ + H+ + 2e-
- FADH2 → FAD + 2H+ + 2e-
- 4H+ + 4e- + O2 → 2H2O (or 2H+ + 2e- + 1/2O2 → H2O)
- Oxygen acts as terminal electron acceptor (reduced as cofactors are oxidized)
-
Phosphorylation of ADP to ATP
- ADP + Pi + H+ → ATP + H2O
- Processes are linked through a proton gradient across the mitochondrial membrane
-
Oxidative Phosphorylation consists of:
- Oxidation of _______ (NADH, FADH2) and reduction of ________
- NADH → ___ + __ + __
- FADH2 → ___ + ___ + ___
- 4H+ + 4e- + O2 → ____ (or 2H+ + 2e- + 1/2O2 → ___)
- Oxygen acts as a ____________
- Phosphorylation of ______
- _____(reaction)_____
- Processes are linked through a ________ across the _______ membrane
Oxidative Phosphorylation consists of:
- Oxidation of reduced cofactors (NADH, FADH2) and reduction of molecular Oxygen (O2)
- NADH → NAD+ + H+ + 2e-
- FADH2 → FAD + 2H+ + 2e-
- 4H+ + 4e- + O2 → 2H2O (or 2H+ + 2e- + 1/2O2 → H2O)
- Oxygen acts as terminal electron acceptor (reduced as cofactors are oxidized)
- Phosphorylation of ADP to ATP
- ADP + Pi + H+ → ATP + H2O
- Processes are linked through a proton gradient across the mitochondrial membrane
The proton gradient is a __________ transport process moving ______ up their concentration gradient using energy from __________
The proton gradient is a primary active transport process moving protons up their concentration gradient using energy from redox reactions within the electron transport chain
Proton gradient is a source of ______ energy
Proton gradient is a source of potential energy
- converts potential energy into chemical energy in the form of a phosphoanhydride bond
Where does Oxidative phosphorylation occur?
Inside the mitochondria
- In and Across the Inner mitochondrial membrane
Compare the pH on the inside of the inner mitochondrial membrane (within the matrix of the mitochondria) against the pH on the outside of the inner mitochondrial membrane (intermembrane space)
- pH of intermembrane space is LOW because ↑[H+]
- pH of matrix is HIGH because ↓[H+]
What are the major components of the Electron Transport Chain?
- Complexes 1-4 (I-IV)
- Integral membrane proteins
- Coenzyme Q
- lipid-soluble coenzyme
- Cofactor (not a protein)
- Cytochrome C (Cyt C)
- Peripheral membrane protein
- involved in transporting e- between complexes III and IV
What are 4 prosthetic groups (cofactors) that participate (ie are reversibly oxidized/reduced during e- transport) in Oxidative Phosphorylation.
Where would you find these prosthetic groups?
- Flavin mononucleotide
- Iron-sulfur clusters
- Copper (Cu2+)
- Cytochrome heme groups
- Found in complexes I-IV as well as in Cytochrome C
Name the lipid-soluble cofactor that acts as a cosubstrate for complexes I, II, and III
Coenzyme Q
How does the affinity for electrons of each cofactor in the electron transport chain assist in transport?
Electrons move from cofactors with lower reduction potential to those with higher reduction potentials
What is the difference between the structures of FAD and Flavin Mononucleotide (FMN)
FAD/FADH2 has an Adenosine whereas FMN does not
What is the reduction reaction of Flavin Mononucleotide (FMN)?
How does it compare to the reduction of FAD to FADH2
FMN + 2H+ + 2e- ←→ FMNH2
Exactly the same as the reduction of FAD to FADH2
(Accepts 2 e- and 2H+)
Iron-sulfur clusters are a way of providing ______ that can be reduced
Iron-sulfur clusters are a way of providing iron atoms that can be reduced
Switch between 3+ and 2+ state by accepting a single e-
What are the components of Iron-Sulfur clusters?
Iron sulfur clusters contain
- Iron
- Sulfur
- Cysteine (Cys) residues
- provide sulfur atoms as part of overall structures
Heme is found as a _________ within a number of the complexes
- complexes that involve the addition of Heme group, as well as cytochrome C, can undergo:
Heme is found as a prosthetic group within a number of the complexes
- complexes that involve the addition of Heme group as well as cytochrome C can undergo: reversible reduction/oxidation to obtain the iron atom found in the heme groups)
- Recall Heme in myoglobin and hemoglobin was non-covalently associated with protein structure
- In this case, there is a covalent bond between the polypeptide chain and the prosthetic group
- Recall Heme in myoglobin and hemoglobin was non-covalently associated with protein structure
What is the most important difference between the heme in cytochrome c vs in hemoglobin/myoglobin?
Most important difference between Heme in cytochrome C vs in myoglobin/hemoglobin is in cytochrome C we
- want the oxidation/reduction process to occur
- whereas part of the role of, say, the proximal histidine in myoglobin/hemoglobin was to change the reduction potential associated with the iron atom to prevent the process of oxidation/reduction
- Protein association allows the heme to act as a proton acceptor or donor in a redox reaction
Coenzyme Q is a cofactor that is very _____\_(contains a large _____\_ portion of its structure in the form of a repeating _____\_)
- Undergoes reduction from _______ to _______ by accepting:
Coenzyme Q is a cofactor that is very hydrophobic (contains a large hydrophobic portion of its structure in the form of a repeating isoprene unit)
- Undergoes reduction from ubiquinone (Q) to Ubiquinol (QH2)
- Net conversion includes accepting 2H+ and 2e-
- Q + 2H+ + e- ←→ QH2
- Net conversion includes accepting 2H+ and 2e-
Because Coenzyme Q is hydrophobic, how might we expect it to behave with the membrane?
Hydrophobic = lipid-soluble
- readily soluble within the hydrophobic portion of the inner mitochondrial membrane
Coenzyme Q is involved with transport of electrons from _________ to _________
Coenzyme Q is involved with the transport of electrons from complexes I and II to Complex III
Redox reactions have a free energy change related to _______
Redox reactions have a free energy change related to reduction potential
What is Reduction Potential?
“affinity for electrons”
- Higher reduction potential → more negative delta G
- Electrons move from compounds with lower reduction potentials to those with higher reduction potentials
Electrons move from compounds with ____\_reduction potentials to those with ____\_ reduction potentials
Electrons move from compounds with lower reduction potentials to those with higher reduction potentials
Higher reduction potential = more negative delta G
How is the formation of the proton gradient an example of primary active transport?
Negative free energy associated with the increase in reduction potential from the redox reactions is used to transport protons across the membrane
- primary active transport process connected to the redox reactions of the electron transport chain
Why is oxygen the terminal electron acceptor?
Oxygen has a very high reduction potential
NADH is reoxidized by the activity of complex ____
NADH is reduced by the activity of complex I
2 e- are passed into complex one and NADH is reoxidized to NAD+
Reoxidation of NADH is associated with the reduction of which component of the electron transport chain?
Complex I is reduced (accepts 2e-)
- Needs to become reoxidized in order to oxidize another NADH
Complex I needs to be reoxidized in order to reoxidize another NADH. How is the reoxidation of Complex I accomploshed?
Complex I interacts with Coenzyme Q (lipid soluble cofactor)
- Coenzyme Q is reduced
- Complex I is (re)oxidized
How does the now reduced Coenzyme Q go from Complex I to Complex III?
Coenzyme Q is lipid-soluble = can move within the bilayer
- Simply “migrates” to Complex III
Once Coenzyme Q reaches Complex III, what happens?
Complex III is reduced (accepts the 2 e-)
Coenzyme Q is reoxidized
Complex III, once reduced, passes the 2e- to ______
Complex III, once reduced, passes the 2e- to Cytochrome C (Cyt C)
- Cytochrome C is reduced
- Complex III is reoxidized
Cytochrome C, as a ____________ protein, is able to migrate from complex ___ on the _____ surface of the inner mitochondrial membrane to Complex ___
Cytochrome C, as a peripheral membrane protein, is able to migrate from complex III on the exterior surface of the inner mitochondrial membrane to Complex IV
Complex IV is reduced by ______ and then passes the electrons to _____ to create _____
Complex IV is reduced by Cytochrome C and then passes the electrons to Oxygen to create water