terminal respiration Flashcards
What do all metabolic pathways lead to the production of?
reduced reactants that act as electron carriers e.g. NADH & FADH2
what is the mitochondria the site of?
oxidative phosphorylation in eukaryotic cells
what do these carriers do?
they make reduced anabolic products or biosynthetic precursors
go through cycles of redox reactions to form ATP
what 2 things do mitochondria allow??
the coupling of the oxidation of carbon fuels to ATP synthesis.
the utilisation of proton gradients to produce ATP (and lots of it).
where do NADH and FADH2 have to be for oxidative phosphorylation to begin?
mitochondrial matrix
what is a shuttle?
it is used to move reducing equivalents across the mitochondrial membrane
what is the glycerol 3 phosphate shuttle/
it allows the NADH synthesized in the cytosol by glycolysis to contribute to the oxidative phosphorylation pathway in the mitochondria to generate ATP.
This happens when NADH reduces Dihydroxy acetone phosphate (DHAP) to Glycerol 3-phosphate (G3-P)
G3-P then passes its electrons to FAD → FADH2 in the mitochondrial matrix
how is an energetic price paid through cytosolic NADH using the Glycerol phosphate shuttle?
Because NADH passes its electrons to FADH2
And the Oxidation of FADH2 yields less ATP than the Oxidation of NADH
what is the electron transport chain?
A game of hot potato (using electrons) passing them around 4 complexes until it reaches O2 as the final electron acceptor to make H2O
While creating a proton concentration gradient (C1 & C3 & C4) between the matrix and the intermembrane.
describe complex I - NADH-Q oxidoreductase (NADH D.H.):
oxidation of NADH:
Reduction of Flavin mononucleotide (FMN) → FMNH2
FMNH2 passes 2e- to ubiquinone (Q) → ubiquinol (QH2)
Pumps H+ ion into the intermembrane space (HIGH ENERGY TRANSITION TO LOW ENERGY)
describe Complex II - Succinate-Q reductase (Succinate D.H.) (Same in Krebs Cycle):
Oxidation of FADH2 → FAD
Reduction of (FMN) → FMNH2
FMNH2 passes 2e- to Q → QH2
Doesn’t pump H+
describe Complex III - Q-cytochrome c oxidoreductase:
Oxidation of ubiquinol (QH2) → ubiquinone (Q)
Reduction of Cyt-c molecules
Pumps H+ ion into the intermembrane space (HIGH ENERGY TRANSITION TO LOW ENERGY)
describe Complex IIII - Cytochrome C oxidase
Oxidation of Cyt-c molecules
Reduction of 1/2 O2
Then 1/2 O2 + 2H+ = H2O
Pumps H+ ion into the intermembrane space (HIGH ENERGY TRANSITION TO LOW ENERGY)
what is ubiquinone/ coenzyme Q10/ Q10?
a coenzyme present in the electron transport chain with 10 isoprene repeats.
It is a dietary supplement that reduces free radicals and acts as an antioxidant.
what is chemiosmosis?
the movement of protons from the mitochondria matrix to the intermembrane of the mitochondria as electrons pass through the complexes of the transport chain.
When the protons flow back down their gradient into the matrix they release energy to do work which is usually stored in the form of ATP, it is known as {{c1::proton motive force}}
what is ATP synthase?
a large multi-unit protein complex that allows protons from the mitochondrial intermembrane to pass through, releasing energy that is stored in the form of ATP (ADP + Pi → ATP).
This is the final step in metabolising the food molecules we eat into energy
- It can produce one ATP for every 3 H+ it moves back into the matrix across the membrane
what are the 2 parts of ATP synthase?
F0 – membrane bound proton conducting unit
– 10 subunits
– Separate subunit connects F0 to F1
F1 – protrudes into the mitochondrial matrix and acts as the catalyst for ATP synthesis
– Produces lots of ATP from the proton motive force energy collected by F0
what’s the importance of the conformational changes (Binding Change Mechanism) in ATP Synthase? and how are they produced?
Conformational changes in the beta subunits of F1 catalyse the ADP → ATP conversion and release ATP.
They are produced by the rotation of the F0 cylinder and gamma shaft.
describe the typical enzyme reaction with ATP:
As long as ATP is still bound to the enzyme, it stays on a low potential energy.
However, detaching the ATP of the enzyme requires high energy.
Which comes from the proton motive force. (proton gradient)
It shows that the proton motive force drives the release of ATP and not the formation of ATP.
Describe what is meant by ‘electron transport chain is uncoupled to ATP synthase’
The electron transport chain is uncoupled to ATP synthesis if:
- The inner mitochondria membrane becomes permeable to protons, so the proton gradient cannot be generated.
- If this happens the electron transport chain still works, with O2 being reduced to H2O, but no ATP is made.
Why does an FADH2 molecule produce less ATP than NADH?
Because FADH2 feeds in at Complex II, so only two sites that move protons across the membrane are utilised. (1.5 mol of ATP)
Because NADH feeds in at Complex I, so three sites are utilised. (2.5 mol of ATP)
Give an example of a disease where the ‘electron transport chain is uncoupled to ATP synthase’
A disease: Malignant hyperthermia
- It is a disease caused by ‘leaky’ mitochondrial membranes that uncouple electron transport and ATP synthase.
what is the proton gradient responsible for?
the coupling of the oxidative process with the ADP phosphorylation process.
what does norepinephrine trigger?
triggers coupling the oxidative process with the ADP phosphorylation process.
