Discussion chapter 7 Flashcards
The citric acid cycle is often described as amphibolic, because ________.
it can operate both in the presence and absence of oxygen
it can oxidize both carbons and nitrogens equally well
it plays a role in both catabolism and anabolism
it is both reversible and irreversible
it plays a role in both catabolism and anabolism
___________________ is the end product of the citric acid cycle’s regeneration phase.
Oxaloacetate.
Select the three citric acid cycle intermediates replenished by anaplerosis in the order they enter the cycle.
- Alpha-Ketoglutarate
2- Succinyl-CoA
3- Oxaloacetate
Which citric acid cycle intermediate is replenished by the following anaplerotic reactions?
1- Carboxylation of pyruvate
2- Transamination of aspartate
3-Transamination of glutamate
1- Oxaloacetate
2-Oxaloacetate
3- Alpha-Ketogluturate
Ethanol is oxidized to form acetate in the liver. Acetate is then converted to acetyl-CoA. How many molecules of ATP would be generated during the conversion of ethanol to acetate? Note that 2 mols of NADH are produced. Assume that one NADH is equivalent to 2.5 ATP and one FADH2 is equivalent to 1.5 ATP molecules.
14
15
5
30
15
Which of the following enzymes catalyze oxidation reactions in the citric acid cycle?
i. Succinate dehydrogenase.
ii. Pyruvate dehydrogenase.
iii. Glycerol-3-phosphate dehydrogenase.
iv. α-Ketoglutarate dehydrogenase.
i, ii, and iv
i and iv
i, iii, and iv
All of the listed enzymes
i and iv
If a suspension of mitochondria is mixed with Antimycin A which inhibits cyt b in complex III, which among the following would increase in concentration?
NAD
Oxidized cytochrome c
Reduced cytochrome c
NADH
Ubiquinol
NADH
The four complexes of the electron transport chain use the energy of electrons stored in reducing agents to create a concentration gradient of protons (H+) across the mitochondrial inner membrane. Give the number of protons pumped into the intermembrane space by each of the four complexes:
complex I:
complex II:
complex III:
complex IV:
- 4H+
- 0
- 4H+
- 2H+
Cyanide blocks electron transport through complex IV. Which of the following will occur if cyanide is added to cells?
O2 consumption will decrease.
The rate of citric acid cycle will increase.
NADH and FADH2 will be depleted.
ATP synthesis will increase.
O2 consumption will decrease.
If the transfer of electrons in tightly coupled mitochondria is inhibited between complex III and complex IV which of the following will occur?
Oxygen consumption will increase.
The H+ ion concentration gradient will be dissipated.
Electron transfer from NADH will stop.
The synthesis of ATP will increase.
Electron transfer from NADH will stop.
Which of the following statements regarding oxidative phosphorylation is TRUE?
The rate of ATP synthesis depends on the magnitude of the proton electrochemical gradient.
The smaller the electrochemical gradient, the faster the Pi- H+ symporter works.
Proton transfer through the Fo subunit of ATP synthase is required in order for ATP synthesis to occur.
The addition of an uncoupler decreases the rate of reoxidation of NADH and FADH2, therefore decreasing the rate of the citric acid cycle.
Proton transfer through the Fo subunit of ATP synthase is required in order for ATP synthesis to occur.
Which of the following are TRUE statements regarding the structure of ATP synthase?
It has a membrane-embedded component called F0 and a component found in the matrix referred to as F1.
The γ subunit acts as the proton “wire” allowing equilibration of the ion gradient.
Research indicates that the F1 portion of the protein rotates in a circular counterclockwise direction.
It has a membrane-embedded component called F0 and a component found in the matrix referred to as F1.
Which of the following describes the isomerization of citrate to isocitrate?
a major regulatory step for the citric acid cycle
an oxidation reaction
the only unnecessary step of the citric acid cycle
protects cells from the toxic effects of arsenite ion
converts a tertiary alcohol that cannot easily be oxidized to a secondary alcohol that can be oxidized
converts a tertiary alcohol that cannot easily be oxidized to a secondary alcohol that can be oxidized
__________________ is the first compound that is oxidized in the citric acid cycle.
Isocitrate
Which of the following enzymes catalyzes a substrate-level phosphorylation?
malate synthase
succinate dehydrogenase
α-ketoglutarate dehydrogenase
succinyl-CoA synthetase
fumarase
succinyl-CoA synthetase
Which reaction below produces GTP in the citric acid cycle?
isocitrate → α-ketoglutarate
α-ketoglutarate → succinyl CoA
succinyl CoA → succinate
fumarate → malate
malate → oxaloacetate
succinyl CoA → succinate
The oxidation of succinate to fumarate is best characterized as an oxidation of _____.
an alkane to an alkene
an alcohol to an aldehyde
an alcohol to a ketone
an aldehyde to a carboxylic acid
a β-keto acid to CO2 and a carboxylic acid that is one carbon smaller
an alkane to an alkene
The reaction catalyzed by fumarase is _____.
an isomerization of an alcohol
a dehydration of an alcohol
a hydroxylation of an alkene
a hydration of an alkene
none of the above
a hydration of an alkene
