Tca Cycle

Front 1

Which combination of cofactors is involved in the conversion of pyruvate to acetyl-CoA?

A. NAD+, biotin, and TPP

B. TPP, lipoic acid, and NAD+

C. pyridoxal phosphate, FAD, and lipoic acid

D. biotin, FAD, and TPP

E. biotin, NAD+, and FAD

Back 1

B

Front 2

True or false

The mechanism of pyruvate dehydrogenase complex is an example of metabolite channeling.

Back 2

True

Front 3

True or false

The citric acid cycle may be viewed as a multi-step catalyst simply because it returns to its original state after each round of reactions.

Back 3

True

Front 4

Which of the following is not required for the oxidative decarboxylation of pyruvate to form acetyl-CoA?

A. NAD+

B. lipoic acid

C. ATP

D. CoA-SH

E. FAD

Back 4

C

Front 5

The role of the Krebs Cycle is to:

A.generates energy directly from acetoacetylCoA, provides NADH for the electron transport chain, and provides energy in the form of ATP from substrate level phosphorylation

B.generates energy directly from pyruvate, provides NADPH for the electron transport chain, and provides energy in the form of ATP from substrate level phosphorylation

C.generates energy directly from acetyl CoA, provides NADH for the electron transport chain, and provides energy in the form of GDP from substrate level phosphorylation

D.generates energy directly from acetyl CoA, provides NADPH for the electron transport chain, and provides energy in the form of ADP from substrate level phosphorylation

E.generates energy directly from acetyl CoA, provides NADH for the electron transport chain, and provides energy in the form of GTP from substrate level phosphorylation

Back 5

E

Front 6

True or false

ATP is consumed by the pyruvate dehydrogenase complex during the synthesis of acetyl CoA.

Back 6

False

Front 7

Which of the following is not an intermediate of the citric acid cycle?

A. oxaloacetate

B. citrate

C. α-ketoglutarate

D. succinyl-CoA

E. acetyl-CoA

Back 7

E

Front 8

The TCA cycle involves the following:

A. eight enzyme catalysed steps, the production of 2 NADH, the production of 1 FADH2, and the production of 1 GTP

B. eight to nine enzyme catalysed steps, the production of 3NADH, the production of 1 FADH2, and the production of 1 GTP

C. eight enzyme catalysed steps, the production of 3 NADH, the production of 2 FADH2, and the production of GTP

D. ten enzyme catalysed steps, the production of 2 NADH, the production of 1 FADH2, and the production of GTP

E. eight enzyme catalysed steps, the production of 2 NADH, the production of 2 FADH2, and the production of GTP

Back 8

B

Front 9

In eukaryotes the enzymes of the citric acid cycle are found in the ________.

A. cytosol

B. mitochondria

C. nucleus

D. endoplasmic reticulum

Back 9

B

Front 10

The anaplerotic reactions related to the citric acid cycle allow the cycle to be:

A. a source of biosynthetic precursers

B. the major pathway for generation of ATP

C. a source of ATP if oxygen is available

D. always based on six-carbon molecules

E. controlled allosterically by ATP

Back 10

A

Front 11

Carbons from acetyl CoA are transferred to the citric acid cycle. Which round of the citric acid cycle could possibly release a carbon atom originating from this acetyl CoA?

Back 11

Second round

Front 12

Which cofactor is not used by the pyruvate dehydrogenase complex?

A. lipoamide

B. thiamine pyrophosphate

C. FAD

D. QH2

Back 12

D

Front 13

Which of the following enzymatic activities would you expect to be decreased by thiamine deficiency?

A. succinate dehydrogenase

B. isocitrate dehydrogenase

C. fumarase

D. pyruvate dehydrogenase

E. malate dehydrogenase

Back 13

D

Front 14

True or false

Pyruvate translocase is specific for transporting pyruvate across the inner mitochondrial membrane.

Back 14

True

Front 15

Few genetic differences in the enzymes of the TCA cycle are known or reported because:

A. no one has studied mutations in the enzymes of the TCA cycle

B. the enzymes are not susceptible to mutations

C. there are too few mutations in these stable enzymes

D. mutations of enzymes in the TCA cycle would be incompatible with life

E. mutations are difficult to detect in TCA enzymes

Back 15

D

Front 16

In mammals, each of the following occurs during the citric acid cycle except:

A. metabolism of acetate to carbon dioxide and water.

B. oxidation of acetyl-CoA.

C. formation of α-ketoglutarate.

D. net synthesis of oxaloacetate from acetyl-CoA.

E. generation of NADH and FADH2.

Back 16

D

Front 17

A deficiency in thiamine causes the disease beriberi. Which might you expect to have a higher than normal blood concentration in an individual with this condition?

A. glucose

B. isocitrate

C. pyruvate

D. oxaloacetate

E. acetyl CoA

Back 17

C

Front 18

The arrangement of subunits in the PDH(pyruvate dehydrogenase) complex ensures that ________.

A. ATP is formed

B. the product of one enzyme is delivered to the next in turn

C. the dihydrolipoamide arm can react with NAD+

D. acetyl CoA enters into the series of reactions

Back 18

B

Front 19

True or false

The overall goal of the citric acid cycle is to oxidize pyruvate, form reduced coenzymes, and produce ATP.

Back 19

True

Front 20

The citric acid cycle oxidizes pyruvate, and some of the pathway intermediates are starting materials for many biosynthetic pathways. This means the citric acid cycle is ________.

A. amplifying

B. amphiteric

C. amphibolic

D. anaplerotic

Back 20

c

Front 21

Which of the following cofactors is required for the conversion of succinate to fumarate in the citric acid cycle?

A. ATP

B. biotin

C. FAD

D. NAD+

E. NADP+

Back 21

C

Front 22

A research student isolates all the enzymes of the TCA cycle and adds oxaloacetate and acetyl CoA. The student also adds the appropriate energy precursors, cofactors, and water. Which of the following will most likely not be a direct product of the experiment?

A. ATP

B. GTP

C. NADH

D. CO2

E. FADH2

Back 22

A

Front 23

Most of the energy released in citric acid cycle reactions is conserved in ________.

Back 23

NADH

Front 24

True or false

The carbon atoms that enter the citric acid cycle via acetyl CoA are the same ones released as carbon dioxide during one round of the citric acid cycle.

Back 24

False

Front 25

True or false

The citric acid cycle is an anaerobic pathway that occurs in the mitochondria of eukaryotes.

Back 25

False

Front 26

Pyruvate translocase is a protein that transports ________.

A. pyruvate and H+ in opposite directions

B. only pyruvate

C. pyruvate and H+ in the same direction

D. pyruvate and CO2 in opposite directions

Back 26

C

Front 27

The conversion of 1 mol of pyruvate to 3 mol of CO2 via pyruvate dehydrogenase and the citric acid cycle also yields _____ mol of NADH, _____ mol of FADH2, and _____ mol of ATP (or GTP).

Back 27

4

1

1