biochem chapter 19 (exam 4)
complex III is composed of
- Iron-sulfur clusters - Cytochrome b and cytochrome c - Hemes
complex II is composed of
- Phosphatidylethanolamine - Hemes - Ubiquinone - Fe-S centers
What are the 2 components of PMF?
- chemical potential - electrical potential
Structure ATP synthase: F0 is an
- integral membrane complex, transports protons from IMS to matrix -dissipating the proton gradient -energy transferred to F1 is used to catalyze phosphorylation of ADP.
molecules present in complex II (Succinate dehydrogenase):
-FAD -Fe-S
molecules present in complex I (NADH dehydrogenase):
-FMN -Fe-S
molecules present in Cytochrome c:
-Heme
molecules present in complex IV (Cytochrome oxidase):
-Hemes -CuA -CuB
molecules present in complex III (Ubiquinone: cytochrome c oxidoreductase):
-Hemes -Fe-S
The end product of ETC include:
-NAD+ -FAD -H2O -ATP -H+
complex IV is composed of
-Protein with 13 subunits -Two heme groups (a and a3) -Copper ions: CuA & CuB
Heme C:
-covalently bound to the protein of cytochrome c through thioether bonds to two Cys residues
Heme A:
-found in a-type cytochromes -has a long isoprenoid tail attached to one of the five-membered rings
Complex I is composed of
-over 40 different polypeptide chains -noncovalently bound FMN -several iron-sulfur center
Example of inhibitors of ETC:
-rotenone -antimycin A -CN- or CO
Examples of inhibitor of ATP synthesis/synthase:
-venturicidin -oligomycin
Uncouplers of ETC:
DNP
Complex II pumps
Does not transfer/pump protons into intramembranous space
What happens to oxygen in ETC?
Oxygen is the final electron acceptor in the ETC; Four electrons are used to reduce one oxygen molecule at complex IV resulting in the formation of 2 water molecules.
Complex II-
Succinate Dehydrogenase
Where does FADH2 enter the chain?
Succinate Dehydrogenase (a.k.a. Complex II)
each complex of electron transport chain (ETC) contains multiple redox centers consisting of:
i. Flavin mononucleotide (FMN) or flavin adenine dinucleotide (FAD) ii. Cytochromes a, b, or c iii. Iron-sulfur cluster
Location of cytochrome a is
in the inner mitochondrial membrane
Location of cytochrome b is
in the inner mitochondrial membrane
Location of electron transport complexes I, II, II and IV in the living cell:
in the inner mitochondrial membrane
PMF is responsible for:
inducing conformational change in the ATP synthase that finally results in ATP synthesis.
location of ETC complexes:
inner membrane
Cytochrome c can freely move in the:
intra membranous space
Electrons are passed, one at a time, via ______________________________________, which becomes reduced to QH2.
iron-sulfur centers to ubiquinone
Ubiquinone:
lipid-soluble conjugated dicarbonyl compound that readily accepts two electrons
Matrix:
lower proton concentration (higher pH)
location of the citric acid cycle and parts of lipid and amino acid metabolism:
matrix
intra membranous:
space between the inner and outer membrane
mitochondrial matrix:
space enclosed by inner membrane
Cytochrome c is present on:
the inner membrane
Role of UCP-1 in babies and hibernating animals:
this uncoupling protein generates heat
Q Cycle:
Four protons are transported across the membrane per two electrons that reach cytochrome c.
Dimers can exist in three different conformations:
1) open: empty 2) loose: binding ADP and Pi 3) tight: catalyzes ATP formation and binds product
How many electrons NADH transfer to electron transport complexes?
2 electrons
Complex III pumps
4 more protons pumped from matrix to intramembranous space
Complex I pumps
4 protons from matrix to intermembrane space
Ubiquinone (fully oxidized) ----> Semiquinol radical:
Addition of H+ + electron
a. Semiquinol radical ----> quinol (fully reduced) :
Addition of H+ + electron
Why NADH forms more ATP molecules than FADH2 a. Because NADH transports 10 H whereas HADH2 transports only 6H. Roughly 3H are required for making one ATP. b. Because NADH transports 6 H whereas HADH2 transports only 10H. Roughly 3H are required for making one ATP.
Because NADH transports 10 H whereas HADH2 transports only 6H. Roughly 3H are required for making one ATP.
Iron-sulfur clusters:
Coordinating by cysteines in the protein; contain equal number of iron and sulfur atoms
Complex IV-
Cytochrome Oxidase
inner membrane contains electron complexes involved in
ETC and ATP synthase
How many electrons FADH2 transfer to electron transport complexes?
FAD accepts 2 electrons from succinate
Cytochromes:
Iron coordinating porphyrin ring derivatives
Complex IV pumps
It Does pump protons into intramembranous space.
What is the importance of PMF?
Make ATP-oxidative phosphorylation
2 primary regulators of ETC:
NADH and ADP
in Complex I, electrons pass from
NADH → FMN → iron-sulfur centers → ubiquinone/coenzyme Q
Complex I-
NADH: Ubiquinone Oxidoreductase
Where does NADH enter the chain? NADH:
NADH: Ubiquinone Oxidoreductase (a.k.a. Complex I)
How does it make ATP?
Proton translocation causes a rotation of the F0 subunit and the central shaft gamma----> This causes a conformational change within all the three alpha beta pairs. ---->The conformational change in one of the three pairs promotes condensation of ADP and Pi into ATP.
in Q cycle, two of the four protons come from
QH2
Structure ATP synthase: F1 is
soluble complex in the matrix
Complex III-
Ubiquinone: Cytochrome c Oxidoreductase
loose conformation:
binding ADP and Pi
Mitochondria have
a double membrane & two distinct compartments; intra membranous and mitochondrial matrix
According to chemiosmotic theory
a proton gradient drives the formation of ATP during oxidative phosphorylation
number of ATP formed in TCA cycle a. 1 ATP molecule b. 2 ATP molecules c. 32-24 ATP molecules
a. 1 ATP molecule
which effects the increased levels of hydrogen ions in the inter-membrane space of the mitochondria? a. increase ATP production b. increased levels of water in inter-membrane space c. decreased levels of chemiosmosis d. decreased levels of oxidative phosphorylation
a. increase ATP production
Reactive oxygen species are removed/quenched by ______________which converts O2 into H2O2 and then the H2O2 is converted to H2O by _________________ a. superoxide dismutase; glutathione peroxidase b. glutathione peroxidase; superoxide dismutase
a. superoxide dismutase; glutathione peroxidase
Ubiquinone, after accepting electrons, it picks up ________ to give an alcohol (ubiquinol) a. two protons b. one proton c. three protons d. four protons
a. two protons
number of ATP formed in Glycolysis a. 1 ATP molecule b. 2 ATP molecules c. 32-24 ATP molecules
b. 2 ATP molecules
the copper ion, CuB, in Complex IV transfers ____ electrons to oxygen which reduces the oxygen molecule into ___water molecules. _____ protons are picked up from the matrix in this process a. 2; 4; two b. 4; 2; four c. 4; 4; two d. 2; 2; four
b. 4; 2; four
a deficiency in which of the following within the mitochondrial matrix will not limit a cells rate of oxidative phosphorylation? a. O2 b. a deficiency in any of these will limit the rate of oxidative phosphorylation c. NAD+ d. FADH2
b. a deficiency in any of these will limit the rate of oxidative phosphorylation
number of ATP formed in ETC a. 1 ATP molecule b. 2 ATP molecules c. 32-24 ATP molecules
c. 32-24 ATP molecules
Highest number of ATP molecule are formed during a. glycolysis b. TCA cycle c. ETC
c. ETC
Complexes __________ pump protons into the intramembranous space (3 of them) a. I, II, III b. I, II, IV c. I, III, IV d. II, III, IV
c. I, III, and IV
products of glucose oxidation essential for oxidative phosphorylation are ______ a. pyruvate b. Acetyl co-A c. NADH and FADH2 d. NADPH and ATP
c. NADH and FADH2
The complete reduction of ubiquinone requires ____electrons and ____protons, and occurs in ____ steps through the semiquinone radical intermediate a. two; three; two b. three; two; three c. two; two; two d. three; three; three
c. two; two; two
for formation of water molecule during ETC, the electrons are
carried by ETC to complex IV
tight conformation:
catalyzes ATP formation and binds product
matrix contains
citric acid cycle enzymes
The formation of water during the ETC occurs at
complex IV (cytochrome oxidase)
for formation of water molecule during ETC, the source of electrons come from a. NADH b. FAD c. FADH2 d. NADH and FADH2
d. NADH and FADH2
in electron transport chain electrons are finally transported to a. NADH b. FADH c. ADP d. O2 e. None of the above f. ATP
d. O2
Conformational States: F0 is a_______ arranged in three αβ dimers. a. soluble b. insoluble c. integral membrane d. hexamer
d. hexamer
what phase of cellular respiration has the highest ATP yield? a. gluconeogenesis b. fermentation c. krebs cycle d. oxidative phosphorylation e. glycolysis
d. oxidative phosphorylation
The energy of electron flow is conserved by the concomitant pumping of protons across the membrane, producing an:
electrochemical gradient, the proton-motive force
open conformation:
empty
Cytochrome c is a
mobile carrier and not attached to the membrane or not an integral membrane protein
Coenzyme Q:
mobile electron carrier transporting electrons from Complexes I and II to Complex III
in Complex II, electrons are passed
one at a time from FAD via iron-sulfur centers to ubiquinone, which becomes reduced to QH2
example of iron-sulfur clusters being simpler or more complex:
other centers include inorganic and Cys S atoms (2Fe-2S or 4Fe-4S centers)
Chemiosmotic theory provides the intellectual framework for understanding many biological energy transductions, including:
oxidative phosphorylation and photophosphorylation.
in Complex IV, electrons passes
passes electrons to O2 forming water
Complex III uses 2 electrons from QH2 to
reduce 2 molecules of cytochrome c
Inner Membrane:
relatively impermeable to most small molecules and ions (including H+), with proton gradient across it
Outer membrane:
relatively porous; allows passage of metabolites (small molecules, ions)
in Q cycle, two molecules of QH2 become oxidized,
releasing protons into the IMS
cytochromes differ by
ring additions
inner membrane convolutions called cristae
serve to increase the surface area
intermembrane space (IMS):
similar environment to cytosol; higher [proton] (lower pH)
Iron-sulfur clusters can be
simpler containing a single Fe surrounded by S atoms of four cysteine residues or more complex.
True or false: iron-sulfur clusters have one elector carrier
true
true or false: cytochromes have one-electron carriers
true
