Oxidative Phosphorylation Flashcards
What is the role of the electron transport and atp synthesis pathway?
-Convert reducing agents into ATP.
What is the terminal electron acceptor?
Molecular oxygen (O2).
Where does oxidative phosphorylation occur?
Inner mitochondrial membrane.
how is electron transport and atp synthesis coupled?
The energy released from electron transport transfers protons from the inside the mitochondrion matrix to the intermembrane space; this gradient is used to drive ATP synthesis catalyzed by ATP synthase.
What happens to coenzymes after reacting with the ETC?
They are oxidized.
How many mitochondria do white muscle cells have? Why is this?
Very few, rely on anaerobic glycolysis.
How many mitochondria do red muscle cells have? Why is this?
Many, require lots of ATP.
What is the important protein located on the outer mitochondrial membrane?
Transmembrane protein porin allows free diffusion of ions and water-soluble metabolites.
What is the inner mitochondrial membrane impermeable to?
Proteins and charged molecules/ionic substances.
What are the folds of the mitochondrial inner membrane called?
Cristae.
Where is the pyruvate dehydrogenase complex and enzymes of the CAC located?
Mitochondrial matrix.
What is the chemiosmotic theory?
The concept that the proton gradient drives ATP formation.
When coupled to ADP, how long does respiration occur?
It proceeds rapidly until all ADP is consumed.
What are uncouplers?
Stimulate the oxidation of substrates in the absence of ADP; oxygen uptake proceeds until all oxygen is depleted.
What kinds of oxidation-reduction centers are present on complexes I-IV?
Cofactors such as FAD, FMN, or Q.
Fe-S clusters, heme, and copper.
In what direction do electrons flow through the ETC?
In the direction of increasing reduction potential.
What do the reduction potentials of each redox center fall between?
The strongest reducing agent NADH and the strongest oxidizing agent O2.
What are the functions of coenzyme Q and cytochrome C?
They serve as links between different complexes of the ETC.
Where does Q transfer electrons to/from?
From complex I or II to complex III.
Where does cytochrome c transfer electrons to/from?
To complex IV from complex III.
What does complex IV use electrons for?
The reduction of O2 into water.
Which complexes translocate protons?
I, III, IV.
Which complex does not translocate protons? Why?
Complex II has a reduction potential very similar to FADH and as a result not enough energy is released to pull protons across the membrane.
What is complex II also known as?
Succinate dehydrogenase complex.
How many electrons enter the ETC at a time?
Two at a time.
Where are the flavin coenzymes FMN and FAH reduced?
FMN: I
FAH: II
How many electrons do the reduced FMNH2 and FADH2 donate at a time?
One.
What kind of molecule is Q?
Lipid-soluble, integrated within the membrane,
How many electrons can Q donate? At a time?
2; 1 at a time.
What kind of protein is cytochrome C?
Peripheral membrane protein.
What is the function of complex I?
To catalyze the transfer of two electrons from NADH to Q.
At what point in the ETC does movement go from two-electrons at a time to one electron at a time?
The passover of two electrons in complex I to FMN converts the rate two one electron at a time.
What is the fully reduced state of Q? How many electrons does it carry?
Ubiquinol; two electrons in QH2
How is Q reduced? Where does QH2 release its protons?
It is reduced by gaining electrons from complex I, and pulls protons up from the matrix. QH2 released protons in complex III.
How many protons are translocated in complex I? How does this occur?
4 protons for every pair of electrons passed from NADH to QH2; this mechanism is not clear.
What is the function of complex II?
Complex II accepts electrons from succinate and catalyzes the reduction of Q to QH2.
What is the function of complex III?
Complex III catalyzes the oxidation of QH2 and reduction of cytochrome c.
How many protons are released during the oxidation of two molecules of QH2?
4.
What is the function of complex IV?
This complex catalyzes the oxidation of reduced cytochrome c produced in III; inclludes four-electron reduction of O2 to 2H20.
How many protons are translocated in complex IV?
Four.
Why are only two protons pumped across the membrane by complex IV?
Two protons are required to reduce oxygen to H20.
How many protons are pumped across the mitochondrial membrane by the ETC for every molecule of NADH oxidized?
10
What is the function of ATP synthase?
To catalyze the synthesis of ATP from ADP+Pi.
What are the two components of ATP synthase? What are the functions of each?
F1 (knob): component that contains catalytic subunits to create ATP, this region projects into the matrix.
F0 (stalk): embedded in the membrane, proton channel that drives the formation of ATP.
How many protons are required for each ATP molecule to be synthesized?
3.
How many protons does ATP synthase consume?
4; 3 for the production of ATP and 1 to transport Pi, ADP, and ATP across the inner membrane.
What is the P/O ratio for NADH?
10/4: 2.5
What is the P/0 ratio for succinate? Why?
6/4: 1.5; complex III= 4, complex IV= 2 = 6.
What are the two purposes of catabolic pathways?
- Breakdown larger molecules into smaller building units.
2. Release and temporarily store energy in high-energy molecules (ATP/NTP/NADH/FADH2)
What kind of pathways are oxidative?
Catabolic; metabolizes oxidized as cofactors are reduced, re-oxidation of cofactors generate ATP.
How many electrons does one molecule of NADH carry?
2.
How many electrons does one molecule of FADH carry?
2.
What kind of proteins are complexes I-IV?
Integral membrane proteins.
What is FMN?
Flavin mononucleotide, similar to FAD/FADH2 but does not contain adenosine.
How many electrons can FMN carry?
2.
How many electrons can an iron-sulfur cluster carry?
1.
What is reduction potential?
Affinity for electrons.
Describe the pathway of the ETC from start to finish:
- NADH is oxidized by Complex I, 2 electrons released. Q is reduced and transfers electrons to III. 4 Protons translocated.
- Complex III oxidized Q, reduces Cyt C, 4 protons translocated.
- Complex IV oxidizes cyt c, reduces O2 into H20. 2 protons translocated.
What is the chemical equation for the ETC? ( 1 mol NADH)
NADH + H20 + 1/2 O2 + 2H +2e —> H20 + 10H + NAD+
What kind of transport is the ETC? How?
Primary active transport; redox reactions cause a change in conformation to permit hydrogens.
What is the prosthetic group in complex II?
FAD.
How is newly-synthesized ATP transported from the matrix?
Adenine Nucleotide Translocate and Pi-H symports.
Describe the flow chart of Ox.Phos (Low energy use)
- Low energy usage
- Low ADP/Pi concentrations
- Lower ATP Synthase activity
- Increased proton gradient
- Decreased electron transport
- O2 consumption is dropped.
- NADH and FADH2 concentrations increase. Inhibit CAC and PDH.
Describe the flow chart of Ox. Phos (High energy use):
- High energy usage.
- High concentrations of ADP/Pi
- Increased ATP Synthase activity
- Decrease in proton gradient.
- Increased electron transport.
- Increased concentrations of NADH and FADH2
- Activation of CAC, PDH.
Describe the process of uncoupling:
An integral membrane protein creates a channel for protons to cross the membrane without ATP synthesis, often generating heat.
What tissue contains uncouplers?
Brown adipose tissue.
How does oxygen consumption differ when paired to an uncoupler?
Consumption increases; proton gradient is dissipated faster by a channel.
