Oxidative Phosphorylation Flashcards
1
Q
Describe the three pathways of lipid metabolism
A
- LIPOLYSIS - occurs 12-24 hrs after fasting. Greater energy yield than glucose or protein catabolism
- Glycerol pathway
- Fatty acid conversion to acetyl CoA (beta oxidation)
2
Q
Describe beta oxidation
A
- Acyl CoA enters through inner mitochondrial membrane
- Dehydrogenation to 2-trans-enoyl CoA by AcylCoA dehydrogenase. FADH produced
- Hydration to 3-hydroxyl acyl CoA
- Oxidised to 3-keto acyl CoA by 3-hydroxy dehydrogenase
- Cleavage to acetyl CoA and acyl CoA
3
Q
What is the ETC?
A
- Series of e- carriers on IMM which undergo redox reactions
- Involves 5 complexes which transfer electrons from glycolysis/TCA cycle for ATP synthesis
- Energy released by redox generates electrochemical proton gradient
- Requires oxygen
4
Q
How does the ETC work? PART 1
A
- NADH, FADH donate electrons through complexes
- Each complex becomes reduced on accepting electrons and oxidised as they transfer electrons to next complex
- Complex I/II –> Coenzyme Q –> Complex III –> Cytochrome C –> Complex IV
5
Q
How does the ETC work? PART 2
A
- Final electron acceptor is oxygen and reduced to water
- Energy released allows pumping of protons from matrix to intermembrane space.
- Forms electrochemical proton gradient. Proton concentration in space > proton concentration in matrix
- Protons pumped into matrix by ATP Synthase - energy is used to synthesise ATP
6
Q
What occurs from Complex I to Coenzyme Q?
A
- Complex I (NADH dehydrogenase) contains FMN and Fe-S proteins
- FMN accepts 2e- from NADH and passes it to Fe-S centres
- 2 electrons transferred to Coenzyme Q causing energy release
- Complex I pumps 4H+ across membrane from matrix into intermembrane space
7
Q
What occurs from Complex II to Coenzyme Q?
A
- Complex II (succinate dehydrogenase) accepts 2e- from FADH2 from succinate
- 2 electrons transferred to Q
- Q becomes reduced after receiving 2 electrons each from Complex I/II
- Q is hydrophobic and diffuses freely in lipid membrane. Electrons donated to Complex III
8
Q
What occurs from Complex III to cytochrome C?
A
- Complex III (Cytochrome b-c1) contains Fe-S centre that accept electrons and become reduced
- Complex III transfers e- to Cytochrome C. 4 protons pumped across membrane.
- Cytochrome C transports e- to Complex IV
9
Q
What occurs from Cytochrome C to Complex IV to O2?
A
- Complex IV (Cytochrome C oxidase) contains O2 between Fe and Cu ions
- Complex IV accepts 4e- from Cytochrome C and transfers to oxygen
- O2 + 4H+ + 4e- –> 2H2O
- Complex IV pumps 4H+ to intermembrane space
10
Q
What is the electrochemical proton gradient?
A
- Energy that pushes protons to reenter matrix to equilibrate
- Protons are more attracted to matrix where pH is more basic
11
Q
What is meant by the electrical and chemical potentials?
A
- Electrical potential: intermembrane space is more positive charged than matrix
- Chemical potential: intermembrane space has more protons, more acidic than matrix
11
Q
Describe chemiosmosis.
A
- Protons pumped across membrane into intermembrane space
- Forms electrochemical proton gradient
- CHEMIOSMOSIS - Flow of protons through ATP Synthase from intermembrane space to matrix down this gradient
12
Q
Describe ATP Synthesis. PART 1
A
- F0 ring rotates as protons pass through membrane
- Causes rod to rotate that attach to F1 subunit
- F1 has 3 catalytic ATP binding sites
- ADP + Pi enters binding site of F1 subunit.
13
Q
Describe ATP Synthesis. PART 2
A
- Rotating subunit 120 DEGREES causes conformational change and phosphorylate to produce ATP.
- Active site release ATP and binds next ADP
- Each 360 degree rotation leads to synthesis of 3 ATPs
14
Q
What stimuli can cause a reverse in ATP Synthase activity?
A
- Direction of proton travel depends on electrochemical proton gradient
- Any factors that disturb this gradient e.g proton leakage, ETC damage or hypoxia
- Will cause synthase to reverse. Hydrolyses ATP generated by glycolysis
