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WorksheetsChap 16
Total questions: 22
Worksheet time: 11mins
Which of the following is not true of the reaction catalyzed by the pyruvate dehydrogenase complex?
Biotin participates in the decarboxylation.
Both NAD+ and a flavin nucleotide act as electron carriers.
The reaction occurs in the mitochondrial matrix.The substrate is held by the lipoyl-lysine “swinging arm.”
Two different cofactors containing —SH groups participate.
The reaction occurs in the mitochondrial matrix.
Which of the below is not required for the oxidative decarboxylation of pyruvate to form acetyl-CoA?
ATP
CoA-SH
FAD
Lipoic acid
NAD+
Which combination of cofactors is involved in the conversion of pyruvate to acetyl-CoA?
Biotin, FAD, and TPP
Biotin, NAD+, and FAD
NAD+, biotin, and TPP
Pyridoxal phosphate, FAD, and lipoic acid
TPP, lipoic acid, and NAD
TPP, lipoic acid, and NADProduction of acetyl-CoA (activated acetate)
One of the products of the reactions of the pyruvate dehydrogenase complex is a thioester of
acetate.
The methyl (—CH3) group is eliminated as CO2
The process occurs in the cytosolic compartment of the cell
The pyruvate dehydrogenase complex uses all of the following as cofactors: NAD+, lipoic acid,
pyridoxal phosphate (PLP), and FAD.
The reaction is so important to energy production that pyruvate dehydrogenase operates at full
speed under all conditions.
Which of the following is not true of the citric acid cycle
All enzymes of the cycle are located in the cytoplasm, except succinate dehydrogenase, which is
bound to the inner mitochondrial membran
In the presence of malonate, one would expect succinate to accumulate.
Oxaloacetate is used as a substrate but is not consumed in the cycle.
Succinate dehydrogenase channels electrons directly into the electron transfer chain
The condensing enzyme is subject to allosteric regulation by ATP and NADH
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
Citrate
Fumarate
Isocitrate
Pyruvate
Succinate
Which of the following is not an intermediate of the citric acid cycle?
Acetyl-coA
Citrate
Oxaloacetate
Succinyl-coA
α-Ketoglutarate
In mammals, each of the following occurs during the citric acid cycle except:
formation of α-ketoglutarate
generation of NADH and FADH2.
metabolism of acetate to carbon dioxide and water.
net synthesis of oxaloacetate from acetyl-CoA.
oxidation of acetyl-CoA
Oxaloacetate uniformly labeled with 14C (i.e., with equal amounts of 14C in each of its carbon atoms)
is condensed with unlabeled acetyl-CoA. After a single pass through the citric acid cycle back to
oxaloacetate, what fraction of the original radioactivity will be found in the oxaloacetate?
all
1/2
1/3
1/4
3/4
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:
1 mol of citrate.
1 mol of FADH2
1 mol of NADH.
1 mol of oxaloacetate
7 mol of ATP.
Which one of the following is not associated with the oxidation of substrates by the citric acid cycle?
All of the below are involved
O2 production
Flavin reductio
Lipoic acid present in some of the enzyme systems
Pyridine nucleotide oxidation
The two moles of CO2 produced in the first turn of the citric acid cycle have their origin in the:
carboxyl and methylene carbons of oxaloacetate
carboxyl group of acetate and a carboxyl group of oxaloacetate.
carboxyl group of acetate and the keto group of oxaloacetate
two carbon atoms of acetate.
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?
ATP
Coenzyme A
Lipoic acid
NAD+
Thiamine pyrophosphate
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:
citrate to isocitrate
fumarate to malate.
malate to oxaloacetate.
succinyl-CoA to succinate
α-ketoglutarate to succinyl-CoA
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:
citrate to isocitrate
fumarate to malate
malate to oxaloacetate
succinate to fumarate.
succinyl-CoA to succinate
Which of the following cofactors is required for the conversion of succinate to fumarate in the citric
acid cycle?
ATP
Bioti
FAD
NAD
NADP
In the citric acid cycle, a flavin coenzyme is required for:
condensation of acetyl-CoA and oxaloacetate
oxidation of fumarate
oxidation of isocitrate.
oxidation of malate
oxidation of succinate.
Which of the following intermediates of the citric acid cycle is prochiral?
Citrate
Isocitrate
Malate
Oxaloacetate
Succinate
Citrate synthase and the NAD+-specific isocitrate dehydrogenase are two key regulatory enzymes of
the citric acid cycle. These enzymes are inhibited by:
acetyl-CoA and fructose 6-phosphate.
AMP and/or NAD+
AMP and/or NADH
ATP and/or NAD+
ATP and/or NADH
During seed germination, the glyoxylate pathway is important to plants because it enables them to:
carry out the net synthesis of glucose from acetyl-CoA
form acetyl-CoA from malate.
get rid of isocitrate formed from the aconitase reaction.
obtain glyoxylate for cholesterol biosynthesis
obtain glyoxylate for pyrimidine synthesis
A function of the glyoxylate cycle, in conjunction with the citric acid cycle, is to accomplish the:
complete oxidation of acetyl-CoA to CO2 plus reduced coenzymes
net conversion of lipid to carbohydrate
net synthesis of four-carbon dicarboxylic acids from acetyl-CoA
net synthesis of long-chain fatty acids from citric acid cycle intermediates.
both B and C are correc
The glyoxylate cycle is
a means of using acetate for both energy and biosynthetic precursors.
an alternative path of glucose metabolism in cells that do not have enough O2.
defective in people with phenylketonuria
is not active in a mammalian liver.
the most direct way of providing the precursors for synthesis of nucleic acids (e.g., ribose)
