Ch13 practice
DNP: will inhibit the electron transport chain. will lead to a decrease in metabolic flux through the citric acid cycle. will decrease the amount of glucose utilized in glycolysis. will allow the energy stored in an electrochemical gradient to be converted to heat. All of the above.
will allow the energy stored in an electrochemical gradient to be converted to heat. (correct)
Electrons from NADH: will go through all the complexes will be transported from complex I to complex III by coenzyme Q. produce 1.5 ATP. will be passed to complex II via the Q-cycle. None of the above.
will be transported from complex I to complex III by coenzyme Q. (correct)
Mutation of all D and E amino acids in the c-subunit of ATP synthase to N and Q: would result in a c-ring that would not exhibit conformational changes leading to rotation and subsequent ATP production. will have no effect on ATP synthase as N and Q differ only slightly from D and E. would prevent the "open" conformation from being adopted by all of the αβ-dimers in ATP synthase. would shutdown ATP synthesis but have no effect on the electron transport chain. None of the above.
would result in a c-ring that would not exhibit conformational changes leading to rotation and subsequent ATP production. (correct)
In an experiment similar to Louis Pasteur's described in the last problem you find that yeast in aerobic conditions will consume just as much glucose as yeast in anaerobic conditions IF the compound DNP is present. In addition a notable spike in temperature is measured for the aerobic conditions reaction vessel. Explain these results.
: DNP is an uncoupler of mitochondrial metabolism and leads to the translocation of P-side protons into the N-side without the production of ATP. Thus the electrochemical gradient that is established by the ETC is not leading to the production of nearly the amount of ATP that it would if DNP were absent. To maintain ATP levels the yeast cell must resort to the consumption of more glucose through the glycolytic path. The increase in temperature is a result of the dissipation of energy stored in the proton gradient as heat. (correct)
Electron transport chain
A series of multi-subunit protein complexes that allow electrons to be transferred from NADH to oxygen making water. (correct)
ATP synthase has a very high affinity for ATP. lowers the standard free-energy of ATP as compared to ATP free in solution. Does not exhibit a large positive change in free energy to form the phosphoanhydride bond between ADP and Pi making ATP. Requires energy to remove the newly synthesized ATP from its active site. All of the above.
All of the above. (correct)
NADH produces 2.5 ATP whereas FADH2 produces only 1.5 ATP (assuming certain constraints on ATP synthase c-ring). Which of the following can, in part, explain this difference? NADH transfers two electrons to the electron transport chain whereas FADH2 only transfers one. NADH transfers electrons to coenzyme Q through complex I a process that translocates four protons. FADH2 however transfers electrons to complex II which translocates no protons. The E'° of NADH is lower than the E'° of FADH2. NADH electrons go through the Q-cycle whereas electrons derived from FADH2 skip this cycle resulting in less proton translocation. B) and C).
B) and C). (correct)
FAD
Complex II. (correct)
Cyt a3
Complex IV. (correct)
Given your newfound knowledge of the atomic details of complex IV structure, explain why CO is a potent inhibitor of the electron transport chain.
For the electron transport chain to function electrons from the complexes must be passed to complex IV that then passes electrons to oxygen. For complex IV to pass electrons to oxygen, oxygen must bind to Cyt a3 that is virtually identical in structure and chemical properties to the heme group found in hemoglobin. As discussed in chapter 8, this heme has a very high affinity for carbon monoxide. Thus, CO poisoning, will lead to the CO binding at Cyt a3 preventing oxygen binding and thus inhibiting the entire ETC. (correct)
flavoprotein
Found in complexes I and II, but not III and IV. (correct)
Myothiazol binds complex III at the Qp site preventing electron transfer through the complex. Base upon this which of the following statements is true? Cytochrome c1 will obtain and maintain a reduced state. Oxygen will continue to be reduced however a total of 4 less protons will be pumped by the ETC leading to less ATP synthesis. Complex IV will obtain electrons from ubiquinol rather than cytochrome c. The cell will experience an increased flux through the citric acid cycle to ensure ATP production levels do not decrease. Glycolytic flux and lactate production will both increase.
Glycolytic flux and lactate production will both increase. (correct)
N-side
High pH. (correct)
Louis Pasteur, in an experiment with yeast, recognized that in anaerobic conditions yeast would consume significantly more glucose than yeast in aerobic conditions. Why is this the case?
In aerobic conditions mitochondrial metabolism is functioning and thus each glucose can lead to the production of 30-32 ATP. In anaerobic conditions however, mitochondrial metabolism is shutdown as the terminal electron acceptor for the ETC has been removed leading to the accumulation of NADH and the subsequent inhibition of the citric acid cycle. Thus, the metabolism of each glucose in anaerobic conditions can only lead to the production of 2 ATP through glycolysis and thus to keep up with cellular demand for ATP the yeast cell must consume significantly more glucose. (correct)
An inhibitor of complex I will lead to the eventual shutdown of the entire electron transport chain including complex II. Why might this be the case when you consider that complex II does not receive electrons from complex I?
Inhibition of complex I leads to NADH accumulation that leads to the inhibition of the citric acid cycle. If this cycle is inhibited, then the production of succinate, the initial electron donor for complex II, will also be inhibited; thus complex II will no longer receive electrons in order to continue in electron transport. (correct)
P-side
Low pH. (correct)
The removal of oxygen from a cell: leads to a decrease in the [NADH] within the matrix. leads to the complete oxidation of the electron transport chain. leads to increased ATP production from ATP synthase. will always result in the death of the cell. None of the above.
None of the above. (correct)
ubiquinone
Oxidized form of an electron carrier that moves electrons from complex I and II to complex III. (correct)
Which of the following statements is true concerning the mitochondrial electron transport chain? Redox centers found in complex III will have lower E'° than those found in complex I. ∼21kJ/mol of energy are available (ΔG∼ -21kJ/mol) when moving a proton from the N-side to the P-side. Complex II acts as a bridge between complex I and III. The E'° of a redox center in complex I is lower than the E'° of oxygen. C) and D).
The E'° of a redox center in complex I is lower than the E'° of oxygen. (correct)
Which of the following statements is true? The energy required to transport electrons through the ETC is provided by the proton gradient. The energy required to make ATP at one step is conserved in an electrochemical gradient. Oxygen is not required to make the proton gradient necessary for ATP synthesis in the mitochondria. Electrons that come from the redox reactions in complex II provide more energy than those that come from complex I.
The energy required to make ATP at one step is conserved in an electrochemical gradient. (correct)
Oxidative phosphorylation
The process by which oxygen is consumed in cellular respiration and ATP is made. (correct)
The reactions of the citric acid cycle: are all located in the matrix of the mitochondria and are all catalyzed by globular proteins. accomplish the net synthesis of oxaloacetate from acetyl-CoA. use molecular oxygen to oxidize acetyl-CoA to CO2. are oxygen dependent. both A) and D).
are oxygen dependent. (correct)
FMN
complex I. (correct)
Cyt C1
complex III. (correct)
cytochromes
found in complexes II, III, and IV. (correct)
