Wiley-Chs. 17-19 Flashcards
… catalyzes a substrate-level phosphorylation reaction within the citric acid cycle
succinyl-CoA synthetase
a membrane-bound enzyme of the citric acid cycle that catalyzes an oxidation reaction is….
succinate dehydrogenase
the compound … is a structural analog and competitive inhibitor of the enzyme succinate dehydrogenase
malonate
which of the following coenzymes is required by E1 of the pyruvate dehydrogenase complex for catalytic activity? …
thiamine pyrophosphate
E2 of the pyruvate dehydrogenase complex contains a lipoyl group that is covalently attached via an amide linkage to a … residue on the enzyme
lysine
condensation of …. with oxaloacetate yield citrate
acetyl-CoA
the reaction catalyzed by pyruvate carboxylase is an example of a … reaction because it replenishes the citric acid cycle intermediates that have been siphoned off for use in other reactions
anaplerotic
the isomerization of citrate to isocitrate:
A) is one major regulatory step for the citric acid cycle because it functions as a rate limiting step
B) protects cells from the toxic effects of arsenite ion
C) converts a tertiary alcohol, which cannot easily be oxidized, to a secondary alcohol that can be oxidized
D) is the rxn of the citric acid cycle that occurs spontaneously without enzymatic catalysis
C) converts a tertiary alcohol, which cannot easily be oxidized, to a secondary alcohol that can be oxidized
Which of the following is(are) True concerning the metabolic rxn shown below?
Pyruvate + NAD+ + CoA-SH –> Acetyl-CoA + NADH + H+ + CO2
I. the enzyme that catalyzes this reaction contains a pyridoxal phosphate prosthetic group
II. this reaction is an oxidative decarboxylation
III. The enzyme that catalyzes this metabolic conversion is activated by high concentrations of ATP
II only
which of the following coenzymes is required by the pyruvate dehydrogenase complex for reoxidation of E3?
NAD+
which of the following enzymes of the citric acid cycle is inhibited by ATP?
A. succinyl-CoA synthetase
B. alpha-ketoglutarate dehydrogenase
C. citrate synthase
D. isocitrate dehydrogenase
isocitrate dehydrogenase
which of the following organisms does not utilize the glyxolate cycle?
A. trees B. bacteria C. fungi D. mammals E. all of the above utilize the glyxolate cycle when necessary
D. mammals
which of the following citric acid cycle intermediates can be converted to aspartate via transamination?
oxaloacetate
Consider the following reaction which has a delta G of about +30 kJ/mol:
malate + NAD+ –> oxaloacetate + NADH + H+
in muscle cells, the reaction proceeds as written. which of the following explains how the reaction occurs as written despite the positive value for delta G?
A. it is thermodynamically favored under standard conditions
B. In the cell, it is kinetically favored, even though it’s thermodynamically unfavorable
C. the concentration of malate must be higher than oxaloacetate for this reaction to occur in the cell
D. [H+] must be higher in muscle than under standard conditions, thus altering delta G to delta G’
E. none of the above
C. the concentration of malate must be higher than oxaloacetate for this rxn to occur in the cell
Germinating plant seeds can convert acetyl-CoA (obtained from fatty acids stored as oils) into carbohydrates, whereas animals are incapable of converting fatty acids into glucose. this difference is due to the fact that:
A. plants use the glyoxylate cycle to convert two acetyl CoA to oxaloacetate, a precursor for gluconeogenesis
B. animals have glycogen and don’t need to make glucose from fatty acids
C. animals use the citric acid cycle selectively for energy production, whereas plants primarily use glycolysis
D. plant seeds use photosynthesis to make sugar
A. plants use the glyoxylate cycle to convert two acetyl CoA to oxaloacetate, a precursor for gluconeogenesis
An individual with a shortage of B vitamins (which include thiamine and riboflavin) may feel fatigued as a result of decreased pyruvate dehydrogenase activity. which of the following would be TRUE regarding this shortage?
A. the amount of acetyl CoA produced from carbohydrate metabolism that enters the citric acid cycle would be decreased
B. a decrease in the amount of NADH would likely decrease activity of citrate synthase
C. flux through the citric acid cycle would cease until adequate pyruvate is available
D. none of the above
E. all of the above
A. the amount of acetyl CoA produced from carbohydrate metabolism that enters the citric acid cycle would be decreased
which of the following steps of the citric acid cycle conserves the energy of a high energy thioester bond?
A. the rxn catalyzed by succinate dehydrogenase
B. the rxn that produces oxaloacetate
C. the condensation rxn that produces citrate
D. the rxn catalyzed by alpha-ketoglutarate dehydrogenase
E. the conversion of citrate to isocitrate
D. the rxn catalyzed by alpha-ketoglutarate dehydrogenase
which of the following enzymatic rxns is favorable both under physiological conditions and under standard conditions?
A. the rxn catalyzed by isocitrate dehydrogenase
B. the rxn catalyzed by malate dehydrogenase
C. the rxn catalyzed by succinate dehydrogenase
D. all of the above
E. none of the above
A. the rxn catalyzed by isocitrate dehydrogenase