Ch 18 Lecture 1
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Within pathway, there are two conversions.
electrons--> proton motive force
proton gradient--> phosphoryl transfer potential
You only have __ ATP in your bony.
How much do you need?
How much do you get from eating 2000 calories.
- 250 grams of
- 139 kg ATP
- 274 mol ATP a day
Briefly explain the ETC.
take electrons from CAC and glycolysis and, in a series of steps, maximize energy release
- 4 complexes; multiple electron carriers
- 3 of the four complexes are proton pumps
Electron motive force allows what?
conversion to proton motive force and flow of hyrogen ions back into the membrane through ATP synthase to produce ATP
How did mitochondria come about?
- a single celled organism capable of photosynthesis was engulfed by a larger organism
Most mitochondria have __. All the genes found in every mitochondrial genome is in common with __ by __%.
their own circular genome
What does a voltmeter do?
measures the likelihood of substance to give up electrons.
See where electrons are flowing
Explain the voltmeter's structure?
a solution of 1 M X and 1 M X- connected by an agar bridge to a solution of 1 M H+ in equilibrium with 1 atm H2 gas
What is the purpose of the voltmeter?
measure redox potential (willingness of something to give up electrons)
Explain redox potential in terms of positive and negative.
- more negative: more willing to give up electrons
- more positive: more willing to accept electrons
What's the ultimate electron acceptor?
Why is oxidative phosphorylation useful as opposed to lactic acid for humans?
oxidative phosphorylation releases 52.6 kcal of energy, allowing more ATP to be made. Lactic acid, on the other hand, causes the formation of only 6 kcal of energy
Explain the ETC
- 3 H+ pumping comples I, III, IV
- Complex II is a succinate dehydrogenase complx that does not pump; FADH2 enters here
As electrons pass through each complex, what o they do?
they ping pong from one prosthetic gorup to another
What are the prosthetic groups of NADHQ oxidoreductase,
Succinate Q reductase, Q-cytochrome c oxidoreductase, and cytochrome oxidase
NADH-Q oxidoreductase: FMN, Fe-S
Succinate Q reductase: FAD, Fe-S
Q-cytochrome c oxidoreductase: Heme bL, bH, heme c1, Fe-S
cytochrome c oxidase (transfers electrons to oxygen): Heme a, a3, CuA and CuB
Explain the forms of ubiquinone.
- Q: ubiquinone
- QH (with dot): semiquinone intermediate
- Q (with dot) - : semiquinone anion radical
- QH2: ubiquinol (two electrons, two protons)
because Q and QH2 are soluble, they can exist in a pool of Q and QH2
NADH transfers its electrons first to __, which then transfers it's electrons to __. Explain the second blank.
- FMN to reduce it to FMNH2
- 3 Fe-S clusters: iron clusters different types moving electrons
What is generally the case for all Fe-S clusters?
they all accept and pass on electrons
Explain succinate dehydrogenase.
- membrane bound (in the mitochondrial membrane)
- two electrons accepted--> tightly bound FADH2, which doesn't leave.
Electrons transferred to Fe-S cluster and then to CoQ (no H+ pumped)
Complex III structure.
dimer of eleven subunits; has series of hemes with iron that keeps transfer
CoQ is __. Cyt C is.
- a two electron carrier
- a one electron carrier that is water solutble in the intermembrane space
Q cycle step one
first reduced QH2 binds in a binding site. It donates one electron to an oxidized Q in another binding site, making it a semiquinone radical ion and donating the other electron to cytC, causing two protons to be pumped. The first QH2 now leaves in an oxidized form.
Q cycle step two.
a different QH2 enters the site. One electron goes to a different Cyt C. The other e- is transferred to the semiquinone radical ion, reducing it to QH2. The QH2 that bound now leaves as oxidized Q.
hemes and copper centers
CuA where cyt c originally drops electrons off.
CuA--> heme a--> heme a3--> CuB
What is the Q cycle formula?
QH2 + 2 cytC (ox) + 2 H+ (matrix)--> Q + 2 cytC (red) + 4 H+ (int.space)
What is the Complex 1 reaction?
NADH+ Q+ 5 H+ (matrix)--> NAD+ + QH2 + 4 H+ (space)
What is the reaction with Complex IV?
What is the goal?
4 e- reduce O2 to water.
- Cyt C docks one at a time.
- First cytC drops off at CuA;
- 1 e- dropped at CuB; another at heme
together, they form the active center and can bind to O2, creating the peroxide bridge.
the goal is to break apart O2, but not released until a safe byproduct is formed.
2 more cytC bind. Same pathway, break bond between 2 oxygen
While __ are used, what happens?
four more protons are pumped
How many protons to break the bond? How many protons to reduce?
How many total?
- two to break
- two to reduce
Overall reaction of complex IV
4 cytC (red) + 8 H+ (matrix) + O2--> 4 cytC (ox) + 2 H2O + 4 H+ (space)
What are the byproducts of the ETC?
H2O and protons
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