The Citric Acid Cycle

Front 1

True or False: FAD is used in the citric acid cycle as an oxidizing agent.

Back 1

True

Front 2

True or False: The final steps in the oxidation of glucose to CO2 occur in the citric acid cycle.

Back 2

True

Front 3

True or False: High concentrations of all intermediates of the citric acid cycle must be present for its efficient operation.

Back 3

False

Front 4

True or False: There are more six-carbon intermediates in the citric acid cycle than four-carbon intermediates.

Back 4

False

Front 5

True or False: In eukaryotes, the enzymes that catalyze the reactions of the citric acid cycle are found in the cytosol.

Back 5

False

Front 6

True or False: Pyruvate is produced in the eukaryotic cytosol but enters the mitochondrial matrix unaided.

Back 6

False

Front 7

True or False: The eukyarotic pyruvate dehydrogenase complex is the largest multienzyme complex known.

Back 7

True

Front 8

True or False: Intermediates of the citric acid cycle that are used for anabolic (synthetic) needs of the cell are replenished by anaplerotic reactions.

Back 8

True

Front 9

True or False: Two moles of coenzyme A are consumed per mole of pyruvate that enters the mitochondria, one in the production of acetyl CoA and the other in the production of succinyl CoA.

Back 9

False

Front 10

True or False: The citric acid cycle is essentially controlled entirely by the availability of acetyl CoA and cycle intermediates.

Back 10

False

Front 11

True or False: Per mole of glucose, the citric acid cycle produces as many high energy phosphate molecules by substrate level phosphorylation as does glycolytic catabolism of glucose to pyruvate.

Back 11

True

Front 12

True or False: The alpha-ketoglutarate dehydrogenase complex is very much like the pyruvate dehydrogenase complex.

Back 12

True

Front 13

True or False: The reaction catalyzed by the succinate dehydrogenase complex is the only step in the citric acid cycle that involves substrate level phosphorylation.

Back 13

False

Front 14

The oxidation of pyruvate to acetyl CoA and CO2 requires the cofactors ___, ___, ___, and ___.

Back 14

coenzyme A
NAD+
FAD
TPP

Front 15

The oxidation of succinate utilizes the enzyme-bound coenzyme ___ due to the need for a stronger oxidizing agent than NAD+.

Back 15

FAD

Front 16

The conversion of isocitrate to alpha-ketoglutarate also produces ___. This is an oxidative process in which the actual oxidant is ___.

Back 16

CO2
NAD+

Front 17

Transformation of pyruvate to acetyl CoA is catalyzed by ___.

Back 17

pyruvate dehydrogenase

Front 18

The enzyme that catalyzes the first step of the citric acid cycle is ___

Back 18

citrate synthase

Front 19

The enzyme that catalyzes the transformation of alpha-ketoglutarate to succinyl CoA is ___

Back 19

alpha-ketoglutarate dehydrogenase

Front 20

The only step in the citric acid cycle that directly produces an energy-rich phosphoanhydride involves the conversion of ___ to ___

Back 20

succinyl CoA
succinate

Front 21

There are a total of ___ oxidation-reduction steps in the catabolism of acetyl CoA via the citric acid cycle. The specific reduced coenzymes formed are ___ and ___

Back 21

four
NADH
QH2

Front 22

Of the eight steps in the citric acid cycle, the number of steps that produce CO2 is ___

Back 22

two

Front 23

A negative modulator involved in regulating each of the enzymes that catalyze the three metabolically irreversible reactions of the citric acid cycle is ___

Back 23

NADH

Front 24

The intermediate ___ is formed by the hydration of ___ in the cycle.

Back 24

L-malate
fumarate

Front 25

If intermediates are removed from the citric acid cycle, they can be replaced by conversion of aspartate into ___ or of glutamate into ___.

Back 25

oxaloacetate
alpha-ketoglutarate