Terminal Respiration Flashcards
Where is most NADH and FADH2 produced?
In the mitochondrial matrix from CAC and beta-oxidation.
Where else is NADH produced?
In the cytosol from glycolysis.
How is NADH transferred to the mitochondrial matrix?
By the glycerol phosphate shuttle:
How does the glycerol phosphate shuttle work?
electrons from NADH transferred to make G-3-P which crosses outer membrane and transfers electrons to form FADH2.
Why is there an energetic cost to using cytosolic reduced substrates in terminal respiraiton?
FADH2 doesnt pass electons throught he 1st complex so produces less ATP than NADH. Therefore theres a cost to using cytosolic NADH as it becomes FADH2.
Why is ubiquinone used as a dietary supplement?
It reduces free radicals so is used as an antioxidant.
Complex 1:
- Oxidises NADH
- e-‘s passed along Fe-S centres
- Produces ubiquinol (QH2) from matrix H+ ions and e-‘s
- 4H+ ions pumped out the matrix
Complex 2:
- Oxidises FADH2
- Fe-S centres channel e-‘s
- Transfers e-‘s to form ubiquinol
Complex 3:
- Ubiquinol from 1&2 gives up electrons to reduce cytochrome c
- Each QH2 reduces 2 cytochrome c molecules
- Pumps 2 protons out the matrix.
Complex 4:
- e-‘s from cytochrome c channled through Fe-Cu centres
- e-‘s pass to O2 which makes water with matrix protons
- 4 more protons pumped through
How many protons are pumped across for every NADH oxidised?
10 H+ ions or protons
How many protons are pumped across for every FADH2 oxidised?
6 H+ ions of protons
What is Chemiosmosis?
Movement of protons down the electrochemical gradient to produce a proton motive force.
Why is chemiosmosis vectoral?
It has a specific directionality of movement
What generates the electrochemical gradient?
The chemical potential (alkaline inside, acidic outside)
The elecrical potential (-ve inside and +ve outside)
What is ATP synthase?
A large multi-subunit protein complex in inner mitochondrial membrane.
Split into F0 and F1
What is the F0?
Membrane bound proton conduction unit.
10 subunits in the channel and 1 connecting to F1 (gamma shaft).
Whats the F0 function?
It captures energy from the proton motive force.
What is the F1?
Protudes into matrix. Made from alpha & beta subunits.
Function of F1?
It uses energy captured by F0 to synthesize ATP
What are the 3 beta subunit types?
- one binds to ATP
- one binds to ADP + Pi
- One cant bind to either
How is ATP synthesised?
- F0 captures energy from proton motive force
- > F0 rotates
- > Gamma shaft rotates
- > Forces conformational changes in beta subunits
How many protons need to pass through ATP synthase for 1 ATP to be made?
3 protons pass through before 1 conformational change occurs.
How much ATP does NADH and FADH2 produce?
Every mole of NADH oxidised forms 2.5 moles of ATP.
One mole of FADH2 oxdisied forms 1.5 moles of ATP.
What is coupling?
Electron transport is said coupled to atp SYNTHEsis.
How does uncoupling occur?
The inner membrane becomes permeable to protons.
Proton gradient cant be generated.
No ATP can be made.
What happens to energy generated by electron transport when uncoupled?
Its released as heat
What is malignant hyperthermia?
A disease caused by leaky membranes when susceptible people are exposed to halothane.
What does a large body temp increase cause?
Irreversible muscle dAMAGE
When does intnetional uncoupling occur in mammals?
When infants are too cold
norepinephrine opens a thermogenin channel in the inner membrane making it leaky to protons
Heat is released to warm up the infant.
(brown fat)
When does intentional uncoupling occur in plants?
Arum lily do it to attract insects to its heat
Skunk cabbage does it to melt snow
