32 Flashcards
Co enzymes capture
Enzymes and energy
Most of the ATP comes from
Oxidative phosphorylation
In the pathway for processing food molecules for ATP synthesis, where is oxygen used?
In oxidative phosphorylation
Oxidative phosphorylation is a ____ process
Coupled
Oxidative phosphorylation is the couples process of:
electron transport through the electron transport chain (ETC)
AND
the phosphorylation of ADP to ATP by ATP-synthase
What are the e lectron transport through the electron transport chain (ETC and the phosphorylation of ADP to ATP by ATP-synthase coupled by?
They are coupled by a proton gradient
The ETC makes the proton gradient
ATP-synthase uses the proton gradient
substrate vs phosphate level
Substrate -energy is coming straight directly from the substrate to make ATP
Oxidative phosphorylation - energy indirectly from the fuel molecule (ETC makes transport gradient that then can be used to make ATP by ATP synthase)
Process of the ETC
- Electrons are passed through a series of carriers
- Electrons from NADH and FADH2 are fed into the electron
transport chain (NADH and FADH2 are oxidized) - These electrons will ultimately reduce molecular oxygen to water
(oxygen is the terminal electron acceptor) - Protons are pumped as the electrons are transported through the
ETC (as electrons are pumped through they release energy) - Builds a proton gradient
Where does the electron transport chain take place and what does it require
- ETC is in the mitochondria (requires oxygen)
- a proton gradient requires a barrier (stops proton diffusion) -
membranes are a barrier to protons - ETC takes place in inner membrane of the mitochondria
how a ETC needs a membrane after you isolate mitochondria from cells- two different tests - one works - one doesn’t.
I DONT UNDERSTAND THIS SLIDE?
Treat with strong detergent
all membranes - ETC does not work (can tell as u are no longer using oxygen and your coenzymes aren’t being oxidised)
→ ETC in a membrane
Treat with mild detergent
Only removes outer membrane ETC still works
→ ETC is in the inner mitochondrial membrane
How many complexes is the ETC organised into? What is the
- ETC organized into four complexes: Complex I to Complex IV
- Each complex contains multiple carriers
- Two mobile carriers: ubiquinone (UQ) and cytochrome c (cyt c)
UQ (ubiquinone) = CoQ (coenzyme Q)
What moves electrons between complex 1,2 and 3?
UQ
What moves electrons between complexes 3 and 4
Cyt c
Don’t need to know the names of the carriers but need to know what the complexes do
Has
Movement of e - through the ____ involves _____ undergoing a series of ______ reactions
ETC
Carriers
Redox
Movement of e - through the ETC involves carriers undergoing a series of redox reactions - how does this work?
Each carrier accepts electron(s) (is reduced) in one redox reaction and then donates electron(s) (is oxidized) in another redox reaction
As electrons move through the carriers, energy is _______
Released
Electrons moves from something with a ____ reduction potential to something with a _____ reduction potential
Low
High
What happens when electrons move to carriers with a higher reduction potential
As electrons move to carriers with a higher reduction potential (oxygen has the highest reduction potential) energy is released (the ΔG0’ is negative)
(- energy is lost
- delta G is positive - so favourable)
What is the energy in the ETC used for?
The energy released in the ETC is used to translocate protons across the mitochondrial inner membrane
(Though the complexes)
(Against conc gradient)
Two ways al electron can flow through the ETC
At the end of the ETC, electrons go into…
Water
Inhibitors of electron flow through the ETC - rotenone
Rotenone inhibits e- transfer from complex 1 to Co-Q
Stop flow of electrons through the ETC No proton gradient formed (ATP not made)
Build-up of reduced co-enzymes (NADH and FADH2)
means no oxidizing power for other pathways
(Last carrier wont be able to pass on electron and become oxidised, therefore second to last carrier wont be able to pass on its electron and so on)
Inhibitors of electron flow through the ETC - Cyanide
Cyanide binds to a carrier in complex IV
Stop flow of electrons through the ETC No proton gradient formed (ATP not made)
Build-up of reduced co-enzymes (NADH and FADH2)
means no oxidizing power for other pathways
(Will inhibit all the way back to the start of the ETC - like a traffic jam as all the carriers ahead of them “stuck” in a reduced form with an electron)
Influences upstream and down stream
Inhibitors of electron flow through the ETC - Carbon monoxide
binds where O2 binds (but carbon monoxide can’t accept electrons)
Stop flow of electrons through the ETC No proton gradient formed (ATP not made)
Build-up of reduced co-enzymes (NADH and FADH2)
means no oxidizing power for other pathways
E lectron flow through the ETC: Complex I
- what happens here>
NADH is oxidized at Complex I
Two e - released into the ETC (travel as a pair)
Four protons are pumped for each NADH oxidized
Electron flow through the ETC: Complex II
FADH2 is oxidized at Complex II
SDH reaction is shared with the citric acid cycle
Two electrons released into the ETC
No protons are pumped
Electron flow through the ETC: UQ
- where does it receive (and how many) electrons from? What can it move within?
Complex I and Complex II both pass two electrons to UQ/ CoQ UQ can move within the inner mitochondrial membrane
The mobile carrier UQ /CoQ
- what is it?
A coenzyme (but not from a vitamin) - our body can make it
The mobile carrier UQ /CoQ - how many forms does it exist in?
Exists in two forms
What does UQ carry?
Carries hydrogen atoms (reducing equivalents)
Whats special about UQ - it can be like half and half… explain?
Co-Q undergoes two-electron redox reactions (like NADH and FADH2), but can accept or release one electron at a time
____ undergoes ________ redox reactions (like NADH and FADH2), but can _______ or ________ one ________ at a time
Co-Q undergoes two-electron redox reactions (like NADH and FADH2), but can accept or release one electron at a time
How are electrons passes to CoQ from complex1 and 2 and how does CoQ release them to complex 3?
Complex I and Complex II both pass two electrons to CoQ Co-Q releases one electron at a time to Complex III (Q-cycle)
Electron flow through the ETC: Complex III
Complex III releases one electron at a time to Cytochrome c Complex III pumps four protons across the inner membrane (for one coenzyme/ two electrons)
Electron flow through the ETC: Cytochrome c
- where does it move?
Moves on outer surface of the inner mitochondrial membrane
Electron flow through the ETC: Cytochrome c
- how many electrons does it carry at a time?
Cytochrome c carries one electron at a time from Complex III to Complex IV
Structure of cytochrome c
- Cytochrome c is a haem (heme) containing protein
- Cytochrome c carries one electron via reversible Fe 2+/Fe3+ redox
reactions
Electron flow through the ETC: Complex IV
Complex IV accepts one electron at a time from Cytochrome c Reduces oxygen to water (terminal electron acceptor)
For 1 NADH/ FADH 2 (2 electrons): 2 H+ pumped
For 1 NADH/ FADH2 (2 electrons): ½O2 + 2H+ → H2O
Biologically the last carrier in Complex IV waits until it has four electrons (oxidation of two coenzymes): O2 + 4H+ → 2H2O
Energy accounting
N ADH: 4 (CI) + 4 (CIII) + 2 (CIV) = 10 protons pumped
FADH2: 4 (CIII) + 2 (CIV) = 6 protons pumped
