Chapter 19 Flashcards
In oxidative phosphorylation, energy from ______ and ______ is used to make ATP
NADH and FADH2
Where does the energy needed to phosphorylate ADP to ATP come from ?
the flow of protons down the electrochemical gradient
In order for the chemiosmotic mechanism to work what must a membrane contain?
- must contain proteins that couple the downhill flow of electrons in the ETC w/ the uphill flow of protons across the membrane
- must contain a protein that couples the downhill flow of proteins to the phosphorylation of ADP
The 4 distinct compartments of the mitochondria
Outer membrane - allows the passage of metabolites
Intermembrane space - higher proton concentration (lower pH)
Inner membrane - relatively impermeable, w/ proton gradient
Matrix - location of CAC, higher pH
_____ and _____ carry electrons from metabolic pathways to the mitochondrial respiratory chain
NADH and FADH2
What drives ATP synthase action?
The electrochemical potential created by proton efflux
What are the 3 types of electron transfers in oxidative phosphorylation
- direct transfer of e-
- transfer as a hydrogen atom (H+ + ee)
- transfer as a hydride ion (H-)
What allows Ubiquinone (Coenzyme Q) to be able to freely diffuse in the inner membrane bilayer (lipid soluble)
It’s isoprenoid side chain
What does Complex I do (NADH: ubiquinone oxidoreductase)
transfers hydride from NADH and a proton from the matrix to ubiquinone
- has a vectorial proton pump
What does a vectorial proton pump do
moves protons in a specific direction from one location to another
- always moves proton from the matrix (negative) to the intermembrane space (positive)
What are inhibitors of complex I
Amytal (barbiturate drug)
rotenone (insecticide)
piercidin A (antibiotic)
What does Complex II (succinate dehydrogenase) do?
oxidizes succinate and reduces ubiquinone
What is Complex III (Cytochrome Bc1) responsible for?
the Q cycle
this part of the mitochondria is porous and allows small molecules and ions to pass
outer membrane
this part of the mitochondria is impermeable to most small molecules and ions including H+, it is the location of the ETC complexes
inner membrane
this part of the mitochondria has an env similar to cytosol and a higher proton concentration
intermembrane space
purpose of iron-sulfur clusters?
they do REDOX b/c transition metals can change oxidation state
- they do one electron transfer reactions
what is a vectorial proton pump?
pump that moves protons from the matrix (-) to the inter membrane space (+)
purpose of Heme B in complex II?
reduces how often electrons leak out
In what complex does the Q cycle occur
Complex III
What compound carries a single electron from the cytochrome bc1 complex (in complex III) to complex IV?
Cytochrome C
- absorbs visible light
What does complex IV do?
reduces O2 to H20, transfers electrons from reduced cytochrome C to oxygen
- it is a dimer
These ions are found in subunit II of complex IV and they resemble (physically and functionally) Fe-S clusters
CuA ions
Name of the supercomplex which contains complexes I,III, IV (II is excluded b/c it needs to be able to feed into the citric acid cycle)
Respirasomes
What are the two components of the proton motive force
chemical potential E - due to difference in concentration of H+ in two regions
Electrical potential E - resulting from separation of charges as protons move across the membrane
What two types of radicals are formed during respiration that create ROS?
superoxide radical
hydroxyl radical
What causes an increase in the generation of ROS?
when the flow of electrons in the respiratory chain is slowed down
What are the molecules that mediate the toxicities of ROS?
Superoxide dismutase (catalyzes the conversion of superoxide and 2H+ into O2 and H202)
Glutathione peroxidase + Glutathione
(convert H202 to H20)
What are the two types of chemical uncoupling agents?
Hydrophobic weak acids (DNP, FCCP)
Ionophores like valinomycin
What blocks complex IV electron transfer to O2 and inhibits respiration and ATP synthesis?
Cyanide
How do hydrophobic weak acids like DNP and FCCP work as chemical uncoupling agents?
they can diffuse across the mitochondrial membrane
- they release protons into the matrix disturbing the proton gradient and therefore disrupting ATP synthase
How do Ionophores like VALINOMYCIN work as chemical uncoupling agents?
they allow inorganic ions to pass through membranes which disrupts the electrical (charge) gradient due to the dissipation of electrical contribution of the proton motive force
What is the role of electron transfer in ATP synthesis?
to create a proton gradient
What are the two domains of ATP synthase ?
Fo and F1
Fo - integral membrane protein, oligomycin sensitive
F1 - peripheral protein and catalytic domain (where the reaction occurs)
The free energy required to release ATP is provided by _____?
the proton motive force
- the release of ATP is highly endothermic since enzyme binds ATP much stronger than ADP
The adenine nucleotide translocase antiporter shuttles ____ out of the matrix while bringing _____ into it
ATP4- goes out into the intermembrane space as ADP3- comes in (this is favored by the electrochemical gradient)
The phosphate translocase symporter shuttles what two molecules into the matrix ?
H+ and H2PO4-
NADH dehydrogenase of Complex I can only accept NADH on the _____ side as NADH is impermeable to the membrane
matrix side
In order to enter the intermembrane space, NADH must be transported in the form of reducing equivalents. What are the possible forms?
oxaloacetate to malate —> oxaloacetate in matrix
oxaloacetate to aspartate
aspartate –> oxaloacetate in the intermembrane space
The complete oxidation of glucose yields more ATP (32 vs 30) via the _____ shuttle
the malate-aspartate shuttle yields more ATP than the Glycerol-3-phosphate shuttle
What is the main regulator of oxidative phosphorylation
[ADP] which is the substrate
- ADP acts as the acceptor of Pi and the rate of O2 consumption depends on the availability of ADP
What are the regulatory proteins of oxidative phosphorylation?
IF1 (inhibitor of F1)
HIF-1 (Hypoxia-inducible Factor)
How does IF1 inhibit F1
it binds to the alpha Beta interface and locks it into place so it cannot rotate around the ATP conformer
What conditions favor regulation by IF1
low pH and hypoxic conditions (occurs when cells are producing ATP via glycolysis b/c then oxidative phosphorylation is not needed)
-when pH increases, IF1 falls off and F1 is reactivated
What conditions cause an increase in HIF-1 expression (and therefore HIF regulation)
low oxygen conditions cause an increase in HIF-1 expression
-HIF-1 acts as a transcription factor and decreases the production of ROS
Explain what “coupling” means in electron transfer and ATP synthesis
coupling refers to the necessary connection b/w mitochondrial ATP synthesis and e- flow through the respiratory chain, neither can proceed without the other
Where does the vectorial pump get the energy needed to pump 4H+ out into the intermembrane space ?
From the electrical work produced as electrons move through the Fe-S clusters
What is the purpose of the Q cycle
the transfer of electrons from ubiquinol (QH2) –> cytochrome C
What are the two different paths taken by the two electrons in Complex III?
one e- goes through Fe-S clusters in the Rieske Center and is then transferred onto the heme group of Cyt C –> Complex IV
the other e- goes to the heme group of Cytochrome B and is then picked up by ubiquinone (Q), Q then gets partially reduced to radial ion Q
What is the difference b/w cytochrome C and Ubiquinone (Q) as an electron carrier?
Cytochrome C can only bind one electron but ubiquinone can bind 2 e-
When does oxidative phosphorylation begin
when electrons enter into the respiratory chain
What is the importance of ubiquinone having an isoprenoid side chain that makes it lipid soluble
lipid soluble means it can diffuse into the inner mitochondrial membrane
– this is important b/c ubiquinone acts as a carrier of protons and electrons throughout complex 1-3
What heme group (a.b.c) is covalently bound to cytochrome and what is it attached to?
C heme is covalently attached to a CYSTEINE
what complex is a citric acid cycle enzyme?
Complex II: succinate dehydrogenase
What are the three components of Complex III (Cytochrome bc1)
cytochrome B, cytochrome C1, Rieske Fe-S protein
