Oxidative Phosphorylation Flashcards
What delivers the electrons to the electron transport chain?
NADH, created by the TCA
What two things determine Eh?
- The Em value (the lower the Em, the lower the Eh)
2. The [red]/[ox] ratio (the higher the ratio, the lower the Eh)
What are the properties of Quinones?
- membrane soluble redox carrier
- can go from fully oxidised to semi to fully reduced (adding e- at a time)
- are hydrophobic so can be inside the membrane (hydrophobic isoprenoid sidechains)
How many electrons do dinucleotides accept/donates?
2
What is the basic structure of dinucleotides?
contains a nictotinamide ring which is where redox occur
How does UQ catalyse its redox reaction
- has to associate with a protein
- attached tightly
Does the semiquinone form detach from the protein? Why?
No, usually remains protein bound
- if they do dissociate from the protein, they become free radicals
- in tissues this may lead to disease such as Alzheimers
Name the biological electron carriers?
substrates and metabolites: - pyruvate/lactate dinucleotides: - NAD+/ NADH -NADP+/NADPH quinones: - ubiquinone/ ubiquinol flavins: - FMN/FMNH2 transition metals: - CU2+/ Cu1+
How many electrons can be accepted/donated by Flavins?
2 e and 2 H can be added in one step, to go fully reduced
- can have semiquinone states
Which type of Haem is a type of cytochrome?
Haemc1
What is cytochrome Haemx?
electron shuttle
What is the most common type of iron-sulphur cluster?
Fe1S0Cys4
- Single iron species (Fe2+/3+)
- surrounded by 4 cysteines
- Cysteinal sulfurs (no inorganic sulfurs)
What are the 3 types of iron clusters in the ETC? Draw them.
Fe1S0Cys4
Fe2S2Cys4
Fe4S4Cys4
What are the properties of the Fe2S2Cys4 cluster?
2 Tetrahedral irons
2 inorganic sulphurs
4 Cysteine side chains
- the transferring electron is delocalised across the whole Fe2S2 cluster
How many electrons can the iron clusters accept each?
Only one at a time
What are the properties of the Fe4S4Cys4 cluster?
4 Tetrahedral irons
4 inorganic sulphurs
4 Cysteine side chains
- orbitals overlap
- the transferring electron is delocalised across the whole cluster
- re-organisation energy, energy is minimised by closing the shape
What influences the mid point potential of an iron sulphur complex?
- environment within the protein structure
What does a low Eh mean?
more likely to donate electron
What are the different ways electrons can be transferred in biological systems?
- electrons transferred intermolecularly
- electron transfer from donor substrate to acceptor cofactor - electrons transferred intramolecularly
- electron jumping between different cofactors in the same protein
- electron jumping from one protein to another
Does distance have a strong influence on the rate that the electrons will be transferred?
Yes. The further apart electrons are, the slower the rate.
What is the key parameter to use for measuring distance between atoms or cofactors?
edge-to-edge distance
- electrons do not sit at the centre of the atom/ can be delocalised across the cofactor
