MCQ CAC Flashcards
Which of the following is not true of the reaction catalyzed by the pyruvate dehydrogenase complex?
A) Biotinparticipatesinthedecarboxylation.
B) Both NAD+ and a flavin nucleotide act as electron carriers.
C) The reaction occurs in the mitochondrial matrix.
D) Thesubstrateisheldbythelipoyl-lysine“swingingarm.”
E) Two different cofactors containing —SH groups participate.
A) Biotinparticipatesinthedecarboxylation.
Which of the below is not required for the oxidative decarboxylation of pyruvate to form acetyl-CoA? A) ATP B) CoA-SH C) FAD D) Lipoicacid E) NAD+
A) ATP
Which combination of cofactors is involved in the conversion of pyruvate to acetyl-CoA? A) Biotin,FAD,andTPP B) Biotin, NAD+, and FAD C) NAD+, biotin, and TPP D) Pyridoxalphosphate,FAD,andlipoicacid E) TPP, lipoic acid, and NAD+
E) TPP, lipoic acid, and NAD+
Which of the following statements about the oxidative decarboxylation of pyruvate in aerobic conditions in animal cells is correct?
A) Oneoftheproductsofthereactionsofthepyruvatedehydrogenasecomplexisathioesterof acetate.
B) The methyl (—CH3) group is eliminated as CO2.
C) The process occurs in the cytosolic compartment of the cell.
D) Thepyruvatedehydrogenasecomplexusesallofthefollowingascofactors:NAD+,lipoicacid,
pyridoxal phosphate (PLP), and FAD.
E) The reaction is so important to energy production that pyruvate dehydrogenase operates at full
speed under all conditions.
A) Oneoftheproductsofthereactionsofthepyruvatedehydrogenasecomplexisathioesterof acetate.
A) Oneoftheproductsofthereactionsofthepyruvatedehydrogenasecomplexisathioesterof acetate.
Allenzymesofthecyclearelocatedinthecytoplasm,exceptsuccinatedehydrogenase,whichis bound to the inner mitochondrial membrane.
Malonate is a competitive inhibitor of succinate dehydrogenase. If malonate is added to a mitochondrial preparation that is oxidizing pyruvate as a substrate, which of the following compounds would you expect to decrease in concentration?
A) Citrate B) Fumarate C) Isocitrate D) Pyruvate E) Succinate
B) Fumarate
Which of the following is not an intermediate of the citric acid cycle?
A) Acetyl-coA
B) Citrate
C) Oxaloacetate D) Succinyl-coA E) α-Ketoglutarate
A) Acetyl-coA
In mammals, each of the following occurs during the citric acid cycle except:
A) formationofα-ketoglutarate.
B) generation of NADH and FADH2.
C) metabolism of acetate to carbon dioxide and water.
D) netsynthesisofoxaloacetatefromacetyl-CoA.
E) oxidation of acetyl-CoA.
D) netsynthesisofoxaloacetatefromacetyl-CoA.
Conversion of 1 mol of acetyl-CoA to 2 mol of CO2 and CoA via the citric acid cycle results in the net production of: A) 1molofcitrate. B) 1 mol of FADH2. C) 1 mol of NADH. D) 1molofoxaloacetate. E) 7 mol of ATP.
B) 1 mol of FADH2.
Which one of the following is not associated with the oxidation of substrates by the citric acid cycle?
A) Allofthebelowareinvolved.
B) CO2 production
C) Flavin reduction
D) Lipoicacidpresentinsomeoftheenzymesystems
E) Pyridine nucleotide oxidation
E) Pyridine nucleotide oxidation
The two moles of CO2 produced in the first turn of the citric acid cycle have their origin in the:
A) carboxylandmethylenecarbonsofoxaloacetate
B) carboxyl group of acetate and a carboxyl group of oxaloacetate.
C) carboxyl group of acetate and the keto group of oxaloacetate.
D) twocarbonatomsofacetate.
E) two carboxyl groups derived from oxaloacetate.
E) two carboxyl groups derived from oxaloacetate.
The oxidative decarboxylation of α-ketoglutarate proceeds by means of multistep reactions in which all but one of the following cofactors are required. Which one is not required? A) ATP B) Coenzyme A C) Lipoic acid D) NAD+ E) Thiaminepyrophosphate
A) ATP
The reaction of the citric acid cycle that is most similar to the pyruvate dehydrogenase complex- catalyzed conversion of pyruvate to acetyl-CoA is the conversion of: A) citrate to isocitrate. B) fumarate to malate. C) malate to oxaloacetate. D) succinyl-CoA to succinate. E) α-ketoglutarate to succinyl-CoA.
E) α-ketoglutarate to succinyl-CoA.
Which one of the following enzymatic activities would be decreased by thiamine deficiency? A) Fumarase B) Isocitrate dehydrogenase C) Malate dehydrogenase D) Succinatedehydrogenase E) α-Ketoglutarate dehydrogenase complex
E) α-Ketoglutarate dehydrogenase complex
The reaction of the citric acid cycle that produces an ATP equivalent (in the form of GTP) by substrate level phosphorylation is the conversion of: A) citrate to isocitrate. B) fumarate to malate. C) malate to oxaloacetate. D) succinate to fumarate. E) succinyl-CoAtosuccinate.
E) succinyl-CoAtosuccinate.
