Chap 16

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.