Flashcards in Mitochondria and oxidative phosphorylation Deck (43)
What type of genome do mitochondria have?
Circular molecule of DNA
What Krebs' Cycle enzyme is located in the mitochondrial membrane and why is it positioned there?
Succinate Dehydrgenase – allows communication with coenzyme Q
Describe the action of cytochrome oxidase
Cytochrome oxidase receives two electrons from cytochrome C Once it has 4 electrons in total, it transfers the four electrons along with 4 protons to Oxygen generating 2H2O
Describe the structure of ATP Synthase.
ATP Synthase has a F0 region (transmembrane)
And a F1 region (protruding into the matrix)
F0 consists of subunits = a, b + c
F1 consists of subunits = , +
Alpha and beta subunits CANNOT rotate because they are fixed in position by a + b subunits
How do redox potentials show that the ETC is energetically favourable?
Each successive membrane complex or carrier has a more positive redox potential than the previous – this means transfer of electrons from one complex to the next is energetically favourable
How does ATP synthase generate ATP?
The gamma subunit rotates forcing the beta subunits to undergo conformational changes which alters their affinities for ADP and ATP Torsional energy flows from the catalytic subunit to the ADP and inorganic phosphate to promote formation of ATP
How does cyanide act as a metabolic poison?
Cyanide binds to Fe3+ in the cytochrome oxidase complex and blocks the flow of electrons through the ETC and consequently, the production of ATP
How does malonate act as a metabolic poison?
Competitive Inhibitor of Succinate Dehydrogenase– slows down the flow of electrons from succinate to ubiquinone by inhibiting the oxidation of succinate to fumarate by succinate dehydrogenase
How does oligomycin act as a metabolic poison?
Binds to the stalk of ATP synthase and inhibits oxidative phosphorylation It blocks the flow of protons through ATP synthase and so causes a backlog of protons in the intermembrane space. The intermembrane space eventually becomes saturated with protons meaning that protons can no longer be pumped into the space by the ETC components. This means that the flow of electrons through the ETC, and hence respiration, stops.
How does dinitrophenol act as a metabolic poison?
Uncouples oxidative phosphorylation from ATP production by transporting protons across the mitochondrial membrane
What is non-shivering thermogenesis?
Thermogenin (UCP-1) channel can be activated in response to a drop in body temperature – like DNP, it allows protons to bypass ATP synthase thereby releasing heat from the dissipation of the proton gradient
***** what is the structure of a mitochondria?
what is the inner membrane for?
what adaptions does it have?
- this is where the electron transport chain happens
- it has a very large surface area due to the folds of the cristae
whatis the evolutionary origin of mitochondria?
- Evolutionary descendant of a prokaryote
- Consumed by eukaryote and an endosymbiotic relationship was established
- many of the genes needed for mitochondrial function were moved to the nuclear genome.
what evidence supports the endosymbiotic theory?
- Mitochondria can only arise from pre-existing mitochondria and chloroplasts
- possess their own genome which resembles that of prokaryotes
- have its own protein synthesising machinery
- The first amino acid of their transcripts is always fMet (formylmethionine) as it is in bacteria
- A number of antibiotics (e.g. streptomycin) that act by blocking protein synthesis in bacteria also block protein synthesis within mitochondria and chloroplasts.
what happens when NADH donates electrons?
- Protons go to the solvent surrounding the enzyme complex.
- Electrons join the Electron Transport Chain.
what happens in oxidative phosphorylation?
: NADH and FADH2 are re-oxidised by molecular oxygen
*****what are the two steps of the chemiosmotic theory?
Oxidative Phosphorylation occurs in two steps:
- the protons move from the matrix of the mitochondria into the space between the mitochondrial membranes
(this is controlled by electron transport)
- Pumped protons are allowed back into the mitochondria through a specific channel which has ATP synthase in it
why do the protons move through the ATP synthase?
due to the pumping of protons into the intermembrane space a gradient is established which is a potential gradient
what does the proton motive force do?
the proton motive force drives the H+ back into the matrix space this consists of a pH gradient AND a transmembrane electrical potential.
what does the electron transport chain consist of?
Consists of three complexes and two mobile carriers which act as electron carriers
what are the membrane complexes?
what are the mobile carriers?
1. NADH Dehydrogenase Complex
2. Cytochrome b-c1 Complex
3. Cytochrome Oxidase Complex
1. Co-enzyme Q (ubiquinone)
2. Cytochrome C
show a diagram of the electron transport chain :
When electrons pass through each complex, protons are pumped to the intermembrane space.
how does ubiquinone work?
an electron carrier, which transfers electron from NADH Dehydrogenase Complex to Cytochrome b-c1.
It can pick up one or two electrons
what is the tail of ubiquinone?
how does cytochrome oxidase work?
cytochrome oxidase is the last membrane complex and it first receives 2 electrons from cytochrome C then it repeats to receives 2 more therefore has 4 electrons.
Cytochrome oxidase passes the electrons to Oxygen to generate water
the 4 electrons are pumped into the inter membrane space
why is oxygen an ideal terminal electron acceptor?
Oxygen is the ideal terminal electron acceptor because it has a high affinity for electrons, proving a driving force for oxidative phosphorylation.
What do negative redox potentials do?
what do positive redox potentials do?
- tendency to donate
- tendency to accept
how is the electron transfer chain energetically favourable?
Each successive membrane complex or carrier has a more positive redox potential than the previous component of the ETC. This means that the transfer of electrons from one complex to the next is energetically favourable.