Metabolism 5 Flashcards
What are the 5 parts of a mitochondrion?
- Cristae
- Intermembrane space
- Inner membrane
- Outer membrane
- Matrix
Where is the location of the ETC?
Inner mitochondrial membrane
Describe the evolutionary origins of mitochondria.
- Evolutionary descendant of prokaryote
- Consumed by a eukaryote - endosymbiotic relationship formed.
- Rickettsia prowazekii are the nearest living descendants of mitochondria
What evidence is there supporting the endosymbiosis theory?
- Mitochondria can only arise from pre-existing mitochondria/chloroplasts
- Mitochondria have their own genome - resembles eukaryotes (circular DNA and no histones associated)
- They have their own protein synthesising machinery
- They share the same start codon as bacteria - fMet
What happens to protons and e- when e- donation occurs by NADH.
Protons go to solvent surrounding enzyme complex
e- go to ETC
Write the equation of oxidation of NADH.
NADH + H+ + 1/2O2 ——-> NAD+ + H20
Write the equation of oxidation of FADH2.
FADH2 + 1/2O2 ——> FAD + H20
What are the 2 steps of oxidative phosphorylation?
- Protons move from mitochondrial matrix to intermembranal space - controlled by ETC
- Pumped protons allowed back into Mitochondrial matrix via specific ATP synthase channels
What are the 2 gradients that contribute to the proton motive force?
Transmembrane electrical potential gradient and pH gradient
What does the ETC consist of?
3 complexes
- NADH Dehydrogenase complex
- Cytochrome b-c1 complex
- Cytochrome Oxidase complex
2 Mobile carriers
- Co-enzyme Q
- Cytochrome C
Each complex has a higher e- affinity than the last, which allows e- to flow in a logical order.
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What happens every time e- pass through each complex?
Protons are pumped to IMS
What does ubiquinone do?
aka co-enzyme Q
transfers e- from NADH Dehydrogenase complex to cytochrome b-c1
Can pick up 1/2 e-
Describe cytochrome oxidase.
The last membrane complex in the ETC.
Receives 2e- from cytochrome C, and then it repeats, so cytochrome oxidase receives 4e- in total.
Cytochrome oxidase then passes the e- to oxygen to generate water.
4 H+ also pumped into IMS, which enhances the proton gradient.
4e- + 4H+ + O2 ———> 2H2O
Why is O2 an ideal terminal e- acceptor?
It has a high affinity for e-.
Negative redox potential means tendency to?
Donate e-
Positive redox potential means tendency to?
Accept e-
Each membrane complex has a more positive redox potential than the last so more energetically favourable e- transfer.
As e- pass along the chain, they lose energy
Describe ATP synthase.
Consists of:
- Membrane bound part (F0).
- Part which projects into matrix (F1)
F0 and F1 have 3 different subunits.
F0 = a, b, c F1 = alpha, beta, gamma
Talk to me about ATP formation using ATP synthase.
- gamma subunit functions as an assymetrical plate.
- Beta subunits consequently undergo structural changes.
- Rotation drives transitions of catalytic portions of Beta subunit, which alters their affinities to ADP and ATP.
- TORSIONAL energy flows from catalytic subunit to ADP and Pi to promote ATP formation.
This can also work in the other direction to hydrolyse ATP and pump protons out of the matrix. (i.e. dependent on direction of proton flow)
FADH2 passes e- directly to ubiquinone (co enzyme Q). What implication does this have?
Fewer protons pumped out so less ATP produced
Cyanide and Azide are metabolic poisons. How do they work?
They bind with high affinity to the Fe3+ form of the haem group present in cytochrome oxidase complex.
They therefore inhibit the cytochrome oxidase complex, by blocking the flow of e- through the respiratory chain.
NO ATP produced as a result
What does CO do?
Binds to the Fe2+ form of the haem group in cytochrome oxidase, so blocks the flow of e-.
Describe malonate.
Malonate very similar to succinate - acts as a competitive inhibitor of succinate dehydrogenase.
Slows down flow of e- from succinate to ubiquinone by inhibiting oxidation of succinate to fumarate.
Describe oligomycin?
- Antibiotic produced by streptomyces - inhibits Oxidative phosphorylation. by binding with ATP synthase stalk.
- Backlog of protons created, which creates a backlog of e-. H+ conc builds up to saturation point in the IMS.
Describe dinitrophenol.
- Weightloss induced by transporting protons across IMS. This causes uncoupling of oxidative phosphorylation from ATP production and so increases BMR and temperature.
What is non-shivering thermogenesis?
UCP-1 (aka thermogenin) is a channel that can be activated to a drop in temp. It allows protons to bypass ATP synthase which releases heat from the dissipation of the proton gradient.
