Download Electron Transport Chain and Oxidative Phosphorylation: Quiz with Solutions and more Exams Health sciences in PDF only on Docsity!
NS 432 0 QUIZ 3 ETC & OX COMIPLDATETEIV E PHOSPHSOLUTIONS!ORY! LATION EXAM WITH
Electron transport chain is a series of -electrons from NADH and FADH2 to oxygen ANSWER intermediate carriers that transfer
Oxidative phosphorylation is a process for -the creation of pH gradient within the mitochondrion as a result of electron transport ANSWER generating ATP; it depends on
Electron transport: electrons carried by ____ are passed through _____ -reduced coenzymes ANSWER
a chain of proteins and coenzymes to drive the generation of a proton gradient acrossthe inner mitochondrial membrane
oxidative phosphorylation: the proton gradient runs... -synthesis of ATP ANSWER downhill to drive the
Both ETC & oxidative phosphorylation occur where? -mitochondrial membrane ANSWER in or at the inner
oxidative phosphorylation -occurring in the mitochondria that results in the formation of ATP from the flow of ANSWER Part of the electron transport chain. A process electrons across the inner membrane to bind with oxygen. Transfer of electrons through the ETC leads to: -from the matrix to the ANSWER the pumping of protons intermembrane space proton gradient is also called the - ANSWER pH gradient
Provides the basis of the coupling mechanism that drives ATP synthesis: -potential (a voltage across the membrane), ANSWER proton gradient, together with the membrane
The electron transport chain consists of: -membrane-bound complexes and two mobile electron carriers (coenzyme Q and ANSWER four multi subunit cytochrome c) The reactions that take place in three of these complexes generate: -energy to drive the phosphorylation of ADP to ATP. ANSWER enough
Many proteins of the ETC contain: -combined with sulfur ANSWER iron, either as part of a heme or
ETC: what shuttles between protein complexes? -(UQ, CoQ) and a water soluble protein (cyt c) ANSWER A lipid soluble coenzyme
energy from oxidation of food materials is funneled into______, the ETC _____ thesecoenzymes & ___- - ANSWER formation of reduced coenzymes (NADH) and reduced flavoproteins (FADH2) re-oxidizes these coenzymes and channels the free energy obtained from thesereactions into the creation of a proton gradient
This re-oxidation process involves removal of: -from the coenzymes ANSWER both protons and electrons
During the electron transport chain the electrons move: -scale from a negative to a more positive reduction potential but the electron carriers do ANSWER down the energy not operate in a simple linear sequence
and electron transport Complexes I and II produce a common product: -which is the substrate for ComplexIII ANSWER reduced coenzyme Q,
Coenzyme Q-cytochrome c reductase - ANSWER complexIII oxidizes UQH2 while reducing cytochrome c, which in turn is the substrate forComplexIV
Cytochrome c oxidase - ANSWER complex IV is responsible for reducing molecular oxygen Complex I: oxidizes ___ & reduce ____ - ANSWER NADH, Coenzyme Q Common name for complex I - ANSWER NADH dehydrogenase First step of complex I involves: -tightly bound FMN ANSWER transfer of electrons from NADH to the
Second step of complex I involves: -reduced FMNH2 to a series of iron-sulfur proteins ANSWER the transfer of electrons from the
Final step of complex I involves: -clusters to coenzyme Q ANSWER transfer of two electrons from iron-sulfur
Path of complex I: - ANSWER NADH --> FMN --> Fe-S --> UQ --> FeS --> UQ
Four H+ transported out per 2 e- Complex II oxidizes ___ & reduces ____ - ANSWER Succinate; Coenzyme Q Complex II is also known as: -enzyme that is an integral membrane protein in the inner mitochondrial membrane ANSWER succinate dehydrogenase, the only TCA cycle
Complex II is composed of: -membrane anchored subunits ANSWER 2 hydrophilic subunits and 2 hydrophobic
3 types of Iron-sulfur clusters, a 4Fe-4S cluster, a 3Fe-4S cluster and a 2Fe-2S cluster When succinate is converted into fumarate in TCA cycle, a concomitant reduction of____ to _____ occurs in succinate dehydrogenase - ANSWER bound [FAD] to [FADH2]
This [FADH2] transfers its electrons immediately to: -which pass them on to coenzyme Q. So the electron flow is from succinate to reduced ANSWER iron-sulfur clusters, coenzyme Q (UQH2) Complex II: 3 types of Fe-S cluster: - ANSWER 4Fe-4S, 3Fe-4S, 2Fe-2S Complex II is also known as: & includes ____ subunits -FAD covalently bound ANSWER flavoprotein 2 (FP2) -
four, including 2 Fe-S proteins Complex II: Path - ANSWER succinate --> FADH2 --> 2Fe2+ --> UQH Complex II net reaction - ANSWER succinate + UQ --> fumarate + UQH
Electron transfer in Complex IV involves: -sites. ANSWER 2 hemes (A & A3) and 2 copper
Electrons from cyt c are used in a ___ -produce 2H2O ANSWER four-electron reduction of O2 to
Oxygen is thus the ____ -transport pathway - the end! ANSWER terminal acceptor of electrons in the electron
Complex IV also transports: - ANSWER H+ Electron transfer through Complex IV begins with binding of: -to the beta barrel of subunit II ANSWER cytochrome c
Complex IV: 4 electrons are transferred sequentially.. -molecules of cytochrome c) first to the CuA center, next to heme a and finally to the ANSWER (one each from four CuB/heme a3 active site, where O2 is reduced to H2O. Coenzyme Q collects electrons from ___ & delivers them by... -reductase (complex I) and succinate-UQ reductase (complex II) ANSWER NADH-UQ
delivers them by diffusion through the membrane core to UQ-cyt c reductase (complexIII)
Cytochrome c is water soluble and moves... -space, carrying electrons from UQ-cyt c reductase to cytochrome c oxidase (complex ANSWER freely in the intermembrane IV). In this process of electron transfers, protons are driven... -membrane from the matrix side to the inter-membrane space ANSWER across the inner
Synthesis of ATP is initiated: steps 1, 2, & 3 -to an L site. ANSWER Step1 by binding of ADP and Pi
Step2 an energy driven conformational change converts the L site to a T conformationand converts T to O and O to L.
Step3, ATP is synthesized at the T site and released from the O site. Two additional passes through this cycle produce two more ATPs and returns theenzyme to its original state
Binding change mechanism for ATP synthesis by ATP synthase: assumes that F1 has: -ANSWER three interacting and conformationally distinct active sites: an open (O) conformation with almost no affinity for ligands, a loose (L) conformation with lowaffinity for ligands, and a tight (T) conformation with high affinity for ligands.
Uncouplers disrupt: -oxidative phosphorylation by dissipating the proton gradient ALLOWING THE ANSWER the tight coupling between electron transport and TRANSPORT TO PROCEED IN THE ABSENCE OF PHOSPHORYLATION Uncouplers are ____ - ANSWER hydrophobic molecules with a dissociable proton Uncouplers carry ____ to dissipate the gradient - ANSWER protons Heat generation by uncoupled mitochondria: -(thermogenin), by providing an alternative route for protons to reenter the mitochondrial ANSWER The uncoupling protein matrix, causes the energy conserved by proton pumping to be dissipated as heat. The free energy of NADH is not conserved as ATP but is: -because oxidation is uncoupled from phosphorylation. ANSWER lost as heat
4 protons translocated by Complex III 2 protons by Complex IV So for each pair of electron that pass through these complexes from NADH2 to O2, atotal of ____ protons are moved across the membrane - ANSWER 10 protons are moved across the membrane P/O for succinate is only ___ because -oxidation do not pass through Complex I ANSWER 6; electrons contributed by succinate
P/O Ratio answers the question -through the chain? ANSWER How many ATP made per electron pair
ETC yields: - ANSWER 10 H+ pumped out per electron pair from NADH to oxygen ____ flow back into matrix per ATP to cytosol - ANSWER 4 H+ P/O Ratio for electrons entering as NADH -as NADH ANSWER 10/4 = 2.5 for electrons entering
P/O Ratio: For electrons entering as succinate (FADH2), -per electron pair to oxygen ANSWER about 6 H+ pumped
6/4 = 1.5 for electrons entering as FADH Shuttle systems effect: - ANSWER electron movement without actually carrying NADH Glycerophosphate shuttle stores electrons in: -electrons to FAD ANSWER glycerol-3-P, which transfers
Glycerophosphate shuttle: first step -transfers its electrons to dihydroxyacetone phosphate to form glycerol-3-phosphate ANSWER NADH produced in the cytosol
G-3-P enters the ___ is then reoxidizes into ___ -through a porin ANSWER intermitochondrial space
dihydroxyacetone phosphate by an FAD- dependent mitochondrial membrane glycerol3- phosphate dehydrogenase.
Glycerophosphate shuttle: the electrons of NADH are -form FADH2. ANSWER transferred to FAD to
The two electrons bound by the FADH2 are transferred directly to coenzyme Q formingQH
QH2 carries the electrons to complex III. Result of glycerophoshate shuttle: - ANSWER 1.5 ATP/NADH Malate-aspartate shuttle uses: -membrane ANSWER malate to carry electrons across the
malate-aspartate shuttle: Step 1: Malate is transported across the -mitochondrial membrane by the dicarboxylic acid or tricarboxylic acid carrier. ANSWER inner
Malate-aspartate shuttle: Step 2: now in the matrix, the malate is -by malate dehydrogenase to generate oxaloacetate and NADH which can now transfer ANSWER reoxidized its electrons to Complex I. Malate-aspartate shuttle: Step 3: the oxaloacetate is transaminated by.. -glutamine to form aspartate and α-ketoglutarate. ANSWER
Therefore species that must cross the inner membrane: such as ____ are carried by ___(2) - ANSWER ions, substrates, fatty acids for oxidation etc
specific transport proteins The inner membrane is extensively folded and the folds are known as ____ which ____ -ANSWER Cristae which provide the inner membrane a large surface area
NADH-CoQ Reductase facts: 2 (EM) - ANSWER Electron transfer from NADH to CoQ More than 30 protein subunits - mass of 850 kD Complex I: the first step involves binding of ____ & transfer of electrons from ___ to ____(3) - ANSWER NADH to the enzyme on the matrix side of the inner mitochondrial membrane transfer of electrons from NADH to tightly bound FMN Complex I: the second step involves the transfer of electrons from the ___ to a ____ -ANSWER reduced [FMNH2]
to a series of Fe-S proteins, including both 2Fe-2S and 4Fe-4S clusters Complex I: the final step of the reactions involves the transfer of 2 electrons from the ___to ___
The coenzyme Q is a ___ which is highly ____ & ____
As a result it shuttles electrons from ___ to ____ (7) -from the iron-sulfur clusters to coenzymeQ ANSWER transfer of 2 electrons
The coenzymeQ is a mobile electron carrier which is highly hydrophobic and diffusesfreely in the hydrophobic core of the inner mitochondrial membrane
As a result it shuttles electrons from complexI and II to complex III Succinate-CoQ Reductase is also known as -TCA cycle!) ANSWER succinate dehydrogenase (from
In cytochromes of these and similar complexes the iron atom at the center of theporphyrin ring cycles between - ANSWER the reduced Fe2+ (ferrous) and oxidized Fe3+ (Ferric) states The b cytochromes contain -hemoglobin and myoglobin ANSWER iron protoporphyrin IX, the same heme found in
The c cytochrome contain -the covalent attachment to cysteine residues from the associated protein ANSWER heme c derived from iron protoporphyrin IX by
Another heme variation is heme a which contains a -chain on a modified vinyl group and a formyl group in place of one of the methyls ANSWER 15-carbon isoprenoid
Cytochrome a is found in - ANSWER 2 forms in Complex IV of the electron chain As with Complex I, passage of electrons through the Q cycle of Complex III is -ANSWER accompanied by proton transport across the inner mitochondrial membrane
Q cycle facts: (2) - ANSWER The Q cycle is divided into 2 halves.
One electron being passed to ___ and the other transferred to ___ and then to ___ (4) -ANSWER a second molecule of reduced coenzyme Q (UQH2) oxidized at the Qp site
cytochrome c the other transferred to heme bL and then to heme bH In this later half of the Q cycle, however the bH electron is transferred to the With the addition of 2 H+ from the mitochondrial matrix, this produces a ____ which isreleased from the ____ & returns to the ___, _____ the Q cycle (5) - ANSWER semiquinone anion, UQ- at the Qn site molecule of reduced coenzyme Q (UQH2) which is released from the Qn site and returns to the coenzyme Q pool completing the Q cycle Complex III takes up 2 protons from the ____ & releases ____ on the ____ for _____ (4) -ANSWER matrix side of the inner membrane and
releases 4 protons on the cytoplasmic side each pair of electrons that passes through the Q cycle
Another significant feature of this mechanism is that it offers a -way for a 2 electron carrier UQH2 to interact with bL and bH hemes, the Fe-S cluster ANSWER convenient and cytochrome c1 all of which are one electron carriers ATP synthase: F1 consists of 5 ____: - ANSWER polypeptides: α, β,γ, δ, and ε
ATP synthase: F0 includes 3 ____ - ANSWER hydrophobic subunits denoted a, b and c F0 forms the -to drive ATP synthesis ANSWER transmembrane pore or channel through which protons move
F0 subunits: -subunits forms a rotor ANSWER The a and b subunits comprise part of the stator and a ring of c
Proton diffusion through the ____ drives ATP synthesis Two parts of ATP synthase (2) - ANSWER ATP synthase F1 and F Inhibitors of Oxidative Phosphorylation Reveal Insights About the Mechanism (4) -ANSWER Many details of electron transport and oxidative phosphorylation have been learned from studying the effects of inhibitors Rotenone inhibits Complex I - and helps natives of the Amazon rain forest catch fish (Natives have learned to beat the roots of certain trees along river banks, releasingrotenone, which paralyzes the fish, making them easy prey)
Cyanide, azide and CO inhibit Complex IV, binding tightly to the ferric form (Fe3+) of a
