Terminal Respiration Flashcards
what is a hexos
A sugar/sacharride containing 6C’s
What can NAD+/FAD be classed as
Co-reactants - which are reduced by H- (hydride) ions containing high E electrons to form NADH/FADH2
What can then happen with NADH/FADH2?
- Used in anabolism
- Pass their High E e- through series of carrier P to yeild lots of ATP (term resp, oxi phosp, e- trans chain). High E e- eventually combine with O2 and form H2O
Where does oxidative phosphorylation occur in eukaryotes
Mitochondria
What’s the puropose of the mitochondria in relation to oxidative phosphorylation?
Allows coupling of oxidation of carbon fules to ATP sysnthesis
utilises proton gradients to produce ATP
Where must NADH/FADH2 be for terminal respiration
mitochondrial matrix
Where is the majoriyt of NADH/FADH2 formed
in mitochondrial matrix (e.g. CAC and B-oxiation of FA
Where else can NADH be formed
In the cytoplasm from glycolysis
How do we move cytoplasmic NADH into the mitochondrial matrix?
Shuttle used to move reducing equivalents accross the mitochondrial membrane (as cytoplasmic NADH can’t cross), but FADH2 can pass it’s e- onto the ETC withing the mitochondria. Process called glycerol phosphate suttle - reversiable oxidative process
Explain the glycerol phosphate shuttle
- NADH can’t cross mitochondrial membranes
- becomes oxidised to NAD+, reducing Dihydroxy acetone phospate to G3P
- G3P passes these e- across the membrane onto FAD, forming FADH2
- FADH2 can then be oxidised in the ETC
see sheet
How much energy is released by the osidation of FADH2 relative to NADH
Per mol, less ATP is generated by oxidation of FADH2 than NADH in the ETC. This means an energetic price is paid for using cytostosolic reduced co-substrates in terminal respiration
What does the ETC contain (name each)
4 complexes:
1. NADH-Q oxidoreductase
2. Succinate-Q reductase
3. Q-cytochrome c oxidoreductase
4. Cytochrome c oxidase
What does complex 1 NADH-Q oxidoreductase do?
Oxidises NADH and passes high-E e- to ubiquinone to give ubiquinol (QH2). Pumps H+ ions into the intermembranse space
What does complex 2 Succinate-Q reductase do?
Oxidises FADH2 and like 1 passes high-E e- to ubiquinone to give ubiquinol (QH2). Enzyme also part of CAC under guise of succinate dehydrogenase
What is Ubiquinone (Q)
- Called Q10 in mitochondria (as has 10 isoprene repeats)
- AKA coenzymeQ10
- Dietary supplement - reduces free radicals so acts as antioxidant
What does complex 3 Q-cytochrome c oxidoreductase do?
- Take e- from ubiquinol (QH2) annd passes them to cytochrome c (like heam)
- 1 Qh2 is oxidised to yeild 2 reduced cytochrome c moleules
- Pumps protons into intermembrane space
What does complex 4 Cytochrome c oxidase do?
- Take e- from cytochrome c and pass them to O2
- e- channeled through Fe-Cu centre
- Pumps protons into intermembrane space
Where do NADH and FADH2 come from?
- NADH: glycolysis, CAC, B-oxidation
- FADH2: B-oxidation, (and HADH via G3P shuttle)
how is energy conserved from the breakdown of food molecules
Ultimately leads to oxidation of NADH, FADH2, ubiquinone and cytochrome c. Energy further conserved through proton gradient across inner mitochondrial membrane
How is enery stored up in proton grads used?
- Electron Motive Force - (actually proton motive force) - allows proton gradient to work
- A molecular turbin has evolved to harness the E in the proton gradient - ATP synthase
Define Chemisosmosis and proton-motive force
- As e- pass through complexes of the transport chain, protons move from matrix to outside of inner mitochondrial membrane - chemiosmosis
- This movement has particular spatial directionality, so is classed as “vectoral”. Ex of energy transformation.
- Protons on outside of membrane act as a store of Ep
- When they are “allowed” to flow back down their grad they release E - Proton motive force
Explain the process of ATp synthesis
- protons eventually flow down their conc grad back into the mitochondrial matrix
- Only a relatively small number of sites exist on membrane where this happen
- At these sites, multi-unit P called ATPsynthase (ATPase) is found
- ATPase has mechanism to allow protons to pass through
- As they flow, E stored in gradient used to Convert ADP+Pi to ATP
- ATP then stores this Ep and uses it to dow work in cells
What is the structure of ATP synthase like?
Has 2 parts:
1. F0 - membrane bound proton conducting unit (10 subunits)
2. F1 - protudes into the mitochoindrial matric and acts as catalyst for ATP syntheses - produces lots of ATP from P-motive force energy collected by F0
How does ATP synthase work?
- ADP+Pi enter B subunit
- Rotation of F0 cylinder and y shaft causes **conformational ** changes in B subunits of F1
- Catalyses ADP->ATP conversion and release ATP
Explain the binding change mechanis of ATPase (briefly)
- not in course?
Sequential conformationsal changes of B subunit - 3 different binding pockets in 3 different states
By rotaion of F0 cylinder and y shaft all binding pockets run cyclic through the 3 states
Why does NADH produce more ATP than FADH2 - stochiometry of oxidative phosphorylation
As e- pass through ETC, complexes 1,3,4 move total of 8H+ from matrix to outside of membrane. ATPase can produce 1ATP per 3H+ it moves back into the matrix across the membrane.
NADH feeds in at Complex 1 meaning e- pass through all 3 sites aloowing proton movement (Complex 1,3,4)
FADH2 feed in at Complex 2 so only 2 sites where protons move across the membrane are utilised,
Thus, 2.5mol and 1.5mol of ATP generated per mol of NADH and FADH2 respectively
What are the products of respiration?
Food molecules completely broken down to CO2, H2O (and energy)
Some Ep from food molecules “saved” (after being transformed through reduced co-reactants and the terminal respiratory system) and is used to make ATP
What is electron transport said to be coupled to?
ATP synthesis (coupled oxidative phosphorylation)
What happens if e- transport is not couples to ATP synthesis?
If inner mitochondrial membrane becomes permeable to protons: proton grad not generated.
E- transport still occur (O2 reduced to H2O) but no ATP made.
Energy released from e- passing along the terminal respiratory system doesn’t make ATP bu is released as heat
What diesase is caused from uncoupled e- transport and ATP synthase
Malignant hyperthermia - “leaky” mitochondrial membranes
When could intentional uncoupling occur?
brown fat in newborn infants - cells have many mitochondria and if baby cold, nor-epinephrine triggers opening of channel protien called thermogenin which sits on inner mitochondrial membrane of brown fat cells - releases heat
What does the proton gradient act as/do?
Store of energy and drives production of lots of ATP
What 2 states can oxidative phosphorylation be?
Coupled or uncoupled
What can coupling or uncoupling be a result off?
Intentionally or in disease states
What is the final electron acceptor
Oxygen (forms 2 H20)
2 parts of oxidative phosphorylation
- Electron transport chain - first 4 proteins
- Chemiosmosis - ATPsynthase part
