Week 14: (A) Oxidative Phosphorylation Flashcards
What is oxidative phosphorylation?
- High energy electrons (carried by NADH and FADH2) are used to reduce O2 to H2O
- phosphorylation of ADP–> ATP
What is the source of high energy electrons?
NADH & FADH2
What is O2 reduced to?
H2O
What is the high energy electrons from NAD & FADH2 used for?
Their energy is used to pump protons (H+) from the mitochondrial matrix to the intermembrane space
How do these H+ flow back into mitochondrial matrix?
Protons flow back across the membrane, following their concentration gradient
-As a potential energy is made
What is a positive redox potential?
more positive the redox potential, the more readily a molecule is reduced.
What changes in the redox potential when co-factors move down the electron transport chain?
Electrons flow down the electron transport chain. NADH & FADH2 will go from negative to more positive redox potential
what do big jumps in redox potential cause?
equate to big changes in ΔG, meaningful work for the cell
Where does oxidative phosphorylation occur?
inner membrane of the mitochondria
What do the many invaginations in the mitochondrial membrane allow?
increase surface area
allow high conc of enzymes that perform in these e- transport reactions to be concentrated in a space
Are proton pumps close to one another?
YES dues to structure of the membrane
What is the coupling of respiration to ATP synthesis called?
oxidatie phosphorylation
What are the two stages in oxidative phosphorylation?
electron transport & ATP synthesis
What are 3 stages in electron transport?
- Electrons flow from NADH and FADH2 to O2
- Respiratory chain
- Energy is used to pump H+ out of the mitochondrial matrix
What are the 2 stages in ATP synthesis?
- Electrochemical gradient of H+ across mitochondrial inner membrane (osmotic charge)
- Energy stored in this gradient can be used to synthesise ATP
Is electron transport and ATP synthesis catalysed by separate proton pumps?
YES
Where do the e- from?
NADH & FADH2
What pumps, pump e- across the inner mitiochondrial membrane?
complex i, iii & iv
What does the increased positive change in the intermediate space cause?
positive charge
electrostatic attractions & conc gradient
What channel is used for H+ to flow through back into the matrix?
ATP synthase
What does ubiquinone do?
coenzyme Q, rapidly shuttles within membrane
How many of the four respiratory complexes pump H+?
3
How does the chain of pumps create an electron gradient?
Transfer of electrons through the respiratory chain
What membrane are the pumps located?
inner mitochondrial membrane
What has the highest H+ concentration?
intermediate space
What electron field is made?
intermembrane space forms an electrical field with the matrix–> matrix side more negative
due to high H+ charge on outer mitochondrial membrane
What happens if you stop the electron flow through the respiratory chain?
stop the H+ movement thus stop generation of the potential
Why is electron transport energetically favourable?
e- moving from a high to low conc
What is electron transport coupled with?
proton pumping against conc gradient
what is the unfavourable reaction in electron transport chain?
pumping of h+ against conc gradient
What two forces are created by H+ moving against conc gradient?
generates. ..
- Membrane potential (large force)
- Conc gradient (smaller force)
What is osmotic pressure?
concentration gradient of H+ across membrane
What is ATP synthase also called?
mitochondrial ATPase/
F1F0 ATPase
What subunit of the ATP synthase protrudes into the mitochondrial matrix?
F1 sub
What subunit of the ATP synthase protrudes into the inner membrane?
F0 sub
hydrophobic
What 2 sections does the ATP synthase have?
stator (does not rotate)& rotor (rotate)
What subunit contains the proton channel?
F0
What does the flow of protons cause in the rotor unit of ATP synthase?
turns the rotor, confo change leads to ATP synthesis
How does the ATP synthase form ATP from ADP + Pi?
space conformation change when rotor is moving—>rotation forces the ADP + Pi to come together.
When rotation creates enough space again, ATP is released into the matrix
How are spaces created in ATP synthase?
The motor causes Alpha & beta complexes to move in and out.
in contact and not in contact alternatively
What is the P/O ratio?
measurement of the coupling between the ATP synthase & electron transport chain.
How many ATP generated from 1 O2
Number of molecules of inorganic phosphate (Pi) incorporate into ATP per atom of oxygen reduced
How many electrons need to flow to oxygen to reduce it?
2
so… how many ATP do we make per 2 electrons that flow into the process
What does P/O ratio depend on?
depends on which substrate is oxidised
NADH or FADH2
What is the p/o ratio of NADH to NAD+?
2.5
What is the p/o ratio of FADH2?
1.5
eg 2FADH2 generated 3 ATP
What are diseases caused by oxidative phosphorylation?
degenerative disease
OXPHOS disease
mutations in mitochondrial or nuclear DNA
symptoms usually appear in tissue with highest ATP
What tissue has the highest ATP?
nervous system, heart, skeletal muscle, kidney
