Glycolysis and Citric Acid Cycle

Question 1

Which statement is true regarding glycolysis?

Select one or more:

a. It only evolved in higher eukaryotes (including humans).
b. The whole pathway takes place in the cytosol.
c. Its enzymes are present in all human cells.
d. Its first phase consumes 2 ATP per glucose molecules.
e. Its second phase yields 4 ATP and 4 NADH per glucose molecules.

Answer 1

b. The whole pathway takes place in the cytosol.
c. Its enzymes are present in all human cells.
d. Its first phase consumes 2 ATP per glucose molecules.

Question 2

Which statement is true regarding glycolysis?

Select one or more:

a. The whole pathway takes place in the cytosol.
b. The whole pathway is reversible.
c. Its second phase includes 2 kinase and 1 dehydrogenase enzymes.
d. Its first phase consumes 2 ATP per glucose molecules.
e. Its committed step is catalyzed by hexokinase or glucokinase.

Answer 2

a. The whole pathway takes place in the cytosol.
c. Its second phase includes 2 kinase and 1 dehydrogenase enzymes.
d. Its first phase consumes 2 ATP per glucose molecules.

Question 3

Which statement is false regarding glycolysis?

Select one or more:

a. Its committed step is catalyzed by hexokinase or glucokinase.
b. The whole pathway takes place in the cytosol.
c. The whole pathway is reversible.
d. It only evolved in higher eukaryotes (including humans).
e. Its second phase yields 4 ATP and 2 NADH per glucose molecules.

Answer 3

a. Its committed step is catalyzed by hexokinase or glucokinase.
c. The whole pathway is reversible.
d. It only evolved in higher eukaryotes (including humans).

Question 4

Which statement is true regarding the oxidative decarboxylation of pyruvate?

Select one or more:

a. It belongs to substrate level phosphorylation because an ATP is produced.
b. The whole process is catalyzed by an enzyme complex in the mitochondrial matrix.
c. Its enzymes are present in all human cells.
d. Human pyruvate decarboxylase contains biotin prosthetic group.
e. It yields NADH, which can deliver electrons to complex I of the respiratory chain.

Answer 4

b. The whole process is catalyzed by an enzyme complex in the mitochondrial matrix.
e. It yields NADH, which can deliver electrons to complex I of the respiratory chain.

Question 5

Which statement is true regarding the oxidative decarboxylation of pyruvate in human cells?

Select one or more:

a. It cannot occur in anaerobic conditions.
b. It is catalyzed by an enzyme complex in the cytosol.
c. It is an irreversible reaction and it cannot be undone (i.e. pyruvate cannot be regenerated from the products).
d. It yields FADH2, which can deliver electrons to complex II of the respiratory chain.
e. It converts a glucoplastic to a ketoplastic molecule.

Answer 5

a. It cannot occur in anaerobic conditions.
c. It is an irreversible reaction and it cannot be undone (i.e. pyruvate cannot be regenerated from the products).
e. It converts a glucoplastic to a ketoplastic molecule.

Question 6

Which statement is false regarding oxidative decarboxylation of pyruvate in human cells?

Select one or more:

a. It is an irreversible reaction but it can be undone (i.e. pyruvate can be regenerated from the products) by other enzymes.
b. It is catalyzed by a large enzyme complex (E1, E2 and E3) in the cytosol.
c. The process can occur in anaerobic conditions because the complex does not use O2.
d. It belongs to substrate level phosphorylation because an ATP is produced.
e. The prosthetic group of E1 is biotin, which is reoxidized by E3 in each catalytic cycle.

Answer 6

a. It is an irreversible reaction but it can be undone (i.e. pyruvate can be regenerated from the products) by other enzymes.
b. It is catalyzed by a large enzyme complex (E1, E2 and E3) in the cytosol.
c. The process can occur in anaerobic conditions because the complex does not use O2.
d. It belongs to substrate level phosphorylation because an ATP is produced.
e. The prosthetic group of E1 is biotin, which is reoxidized by E3 in each catalytic cycle.

Question 7

Which statement is false regarding oxidative decarboxylation of pyruvate in human cells?

Select one or more:

a. It is catalyzed by homodimers of pyruvate decarboxylase in the mitochondrial matrix.
b. The acetaldehyde intermediate is covalently bound to the enzyme as a hydroxyethyl group.
c. The product, acetate is bound to CoA in a macroergic thioester bond.
d. It is coupled to the mitochondrial electron transfer chain by NAD+ and NADH.
e. It is the last step of anaerobic glycolysis and it produces lactate.

Answer 7

a. It is catalyzed by homodimers of pyruvate decarboxylase in the mitochondrial matrix.
e. It is the last step of anaerobic glycolysis and it produces lactate.

Question 8

Which statement is true?

Select one or more:

a. Oxidative phosphorylation is activated by ATP in starvation.
b. Oxidative catabolic processes in the mitochondrial matrix are coupled to respiration.
c. Citrate cycle is inhibited by high NADH/NAD+ ratio.
d. Pyruvate dehydrogenase is activated by low ATP/ADP ratio.
e. Malate/aspartate shuttle transports electrons from fatty acid oxidation to respiration.

Answer 8

b. Oxidative catabolic processes in the mitochondrial matrix are coupled to respiration.
c. Citrate cycle is inhibited by high NADH/NAD+ ratio.
d. Pyruvate dehydrogenase is activated by low ATP/ADP ratio.

Question 9

Which statement is true?

Select one or more:

a. Citrate cycle cannot function in anaerobic conditions.
b. Fatty acid oxidation takes place in the cytosol.
c. Substrate level phosphorylation occurs both in glycolysis and in citrate cycle.
d. Uncouplers of oxidative phosphorylation cause inhibition of oxidative catabolism.
e. ADP activates oxidative phosphorylation as a substrate of FoF1 ATPase.

Answer 9

a. Citrate cycle cannot function in anaerobic conditions.
c. Substrate level phosphorylation occurs both in glycolysis and in citrate cycle.
e. ADP activates oxidative phosphorylation as a substrate of FoF1 ATPase.

Question 10

Which statement is false?

Select one or more:

a. Substrate level phosphorylation occurs both in glycolysis and in citrate cycle.
b. Uncouplers of oxidative phosphorylation cause inhibition of oxidative catabolism.
c. Pyruvate dehydrogenase and citrate cycle cannot function in anaerobic conditions.
d. ADP activates oxidative phosphorylation as a substrate of FoF1 ATPase.
e. FoF1 ATPase is an active transporter, which can pump protons into the matrix.

Answer 10

b. Uncouplers of oxidative phosphorylation cause inhibition of oxidative catabolism.
e. FoF1 ATPase is an active transporter, which can pump protons into the matrix.

Question 11

Which statement is false?

Select one or more:

a. Citrate cycle does not use O2, therefore it can function in anaerobic conditions.
b. Uncouplers of oxidative phosphorylation cause activation of oxidative catabolism.
c. Oxidative phosphorylation is uncoupled when the inner mitochondrial membrane is permeable for ions.
d. Respiration can be inhibited by KCN when oxidative phosphorylation is uncoupled.
e. Respiration can be inhibited by oligomycin when oxidative phosphorylation is uncoupled.

Answer 11

a. Citrate cycle does not use O2, therefore it can function in anaerobic conditions.
e. Respiration can be inhibited by oligomycin when oxidative phosphorylation is uncoupled.

Question 12

Which is prosthetic group in pyruvate-dehydrogenase complex?

Select one or more:

a. flavine mononucleotide (FMN),
b. CoA,
c. thiamine pyrophosphate (TPP),
d. heme,
e. flavine adenine dinucleotide (FAD).

Answer 12

c. thiamine pyrophosphate (TPP)

e. flavine adenine dinucleotide (FAD).

Question 13

Which cofactor is involved in the oxidative decarboxylation of pyruvate?

Select one or more:

a. CoA,
b. flavine mononucleotide (FMN),
c. CoQ,
d. NAD+,
e. biotine.

Answer 13

a. CoA

d. NAD+

Question 14

Which enzyme contains FAD prosthetic group?

Select one or more:

a. a-ketoglutarate dehydrogenase complex,
b. E3 of PDH complex,
c. mitochondrial glycerol 3-phosphate dehydrogenase,
d. succinate dehydrogenase,
e. malate dehydrogenase.

Answer 14

a. a-ketoglutarate dehydrogenase complex
b. E3 of PDH complex
c. mitochondrial glycerol 3-phosphate dehydrogenase
d. succinate dehydrogenase,

Question 15

Which enzyme contains FAD prosthetic group?

Select one or more:

a. Complex I of the respiratory chain,
b. á-ketoglutarate dehydrogenase,
c. malate dehydrogenase,
d. pyruvate dehydrogenase complex,
e. isocitrate dehydrogenase.

Answer 15

b. á-ketoglutarate dehydrogenase

d. pyruvate dehydrogenase complex

Question 16

Which enzyme uses NAD+/NADH?

Select one or more:

a. Complex I of the respiratory chain,
b. succinate dehydrogenase,
c. malate dehydrogenase,
d. acyl-CoA dehydrogenase,
e. glyceraldehide 3-phosphate dehydrogenase.

Answer 16

a. Complex I of the respiratory chain
c. malate dehydrogenase
e. glyceraldehide 3-phosphate dehydrogenase.

Question 17

Which enzyme produces ATP in glycolysis?

Select one or more:

a. 3-Phosphoglycerate kinase,
b. Phosphofructokinase,
c. Hexokinase,
d. Pyruvate kinase,
e. Pyruvate dehydrogenase kinase.

Answer 17

a. 3-Phosphoglycerate kinase

d. Pyruvate kinase

Question 18

Which enzyme consumes ATP in glycolysis?

Select one or more:

a. 3-Phosphoglycerate kinase,
b. phosphofructokinase,
c. hexokinase,
d. pyruvate kinase,
e. pyruvate dehydrogenase kinase.

Answer 18

b. phosphofructokinase

c. hexokinase

Question 19

Which compound is allosteric activator for phosphofructokinase 1 (PFK1)?

Select one or more:

a. AMP,
b. citrate,
c. fructose 2,6-bisphosphate,
d. glucagon,
e. acyl-CoA.

Answer 19

a. AMP

c. fructose 2,6-bisphosphate,

Question 20

Which compound is allosteric inhibitor for phosphofructokinase 1 (PFK1)?

Select one or more:

a. AMP,
b. citrate,
c. fructose 2,6-bisphosphate,
d. glucagon,
e. acyl-CoA.

Answer 20

b. citrate

e. acyl-CoA.

Question 21

Which activates pyruvate dehydrogenase complex?

Select one or more:

a. acetyl-CoA,
b. ATP,
c. ADP,
d. pyruvate dehydrogenase kinase,
e. Ca2+.

Answer 21

c. ADP

e. Ca2+

Question 22

Which inhibits pyruvate dehydrogenase complex?

Select one or more:

a. CoA,
b. insulin,
c. ADP,
d. pyruvate dehydrogenase kinase,
e. NADH.

Answer 22

d. pyruvate dehydrogenase kinase

e. NADH.

Question 23

What is the right order of intermediates in glycolysis?

Select one or more:

a. 2-bisphosphoglycerate,
b. glyceraldehyde 3-phosphate,
c. dihydroxyacetone phosphate,
d. 3-bisphosphoglycerate,
e. 1-3-bisphosphoglycerate.

Answer 23

a. 2-bisphosphoglycerate,
b. glyceraldehyde 3-phosphate,
c. dihydroxyacetone phosphate,
d. 3-bisphosphoglycerate,
e. 1-3-bisphosphoglycerate.

Question 24

What is the right order of intermediates in citrate cycle?

Select one or more:

a. succinyl-CoA,
b. fumarate,
c. succinate,
d. á-ketoglutarate,
e. malate.

Answer 24

a. succinyl-CoA
b. fumarate
c. succinate
d. á-ketoglutarate
e. malate.

Question 25

What is the right order of electron carriers in the respiratory chain?

Select one or more:

a. cytochrome c,
b. succinate,
c. CuB,
d. ubiquinone,
e. FAD.

Answer 25

a. cytochrome c
b. succinate
c. CuB
d. ubiquinone
e. FAD.

Question 26

What is the right order of electron carriers in the respiratory chain?

Select one or more:

a. cytochrome c,
b. FMN,
c. NADH,
d. CuB,
e. ubiquinone.

Answer 26

a. cytochrome c
b. FMN
c. NADH
d. CuB
e. ubiquinone.

Question 27

Which is the major role of lactate dehydrogenase (LDH) reaction in anaerobic glycolysis?

Select one:

a. production of ATP,
b. elimination of hydrogen,
c. elimination of lactate,
d. regeneration of NAD+,
e. regeneration of pyruvate.

Answer 27

d. regeneration of NAD+

Question 28

Which can be considered as the committed step of glycolysis?

Select one:

a. glyceraldehydes 3-phosphate dehydrogenase,
b. hexose phosphate isomerase,
c. hexokinase / glucokinase,
d. pyruvate kinase,
e. phosphofructokinase 1.

Answer 28

e. phosphofructokinase 1.

Question 29

Which is not involved in oxidative decarboxylation of pyruvate by PDH complex?

Select one:

a. lipoamide,
b. biotin,
c. FAD,
d. CoA,
e. NAD+.

Answer 29

b. biotin

Question 30

Which is not involved in oxidative decarboxylation of pyruvate by PDH complex?

Select one:

a. thiamine pyrophosphate,
b. FAD,
c. NAD+,
d. ubiquinone,
e. CoA.

Answer 30

d. ubiquinone

Question 31

Chose the correct/right sentence regarding hepatic phosphofructokinase1 (PFK1).

Select one:

a. Insulin increases fructose 2,6-bisphosphate level and hence activates PFK1.
b. Insulin decreases fructose 2,6-bisphosphate level and hence activates PFK1.
c. Insulin causes phosphorylation and activation of PFK1.
d. Glucagon causes phosphorylation and activation of PFK1.
e. Glucagon decreases fructose 2,6-bisphosphate level and hence activates PFK1.

Answer 31

a. Insulin increases fructose 2,6-bisphosphate level and hence activates PFK1.

Question 32

Chose the wrong/false sentence regarding hepatic phosphofructokinase (PFK) enzymes.

Select one:

a. Insulin causes dephosphorylation of PFK2 and activation of PFK1.
b. PFK2 uses ATP for irreversible phosphorylation of fructose 6-phosphate.
c. PFK1 is allosterically activated by AMP.
d. PFK1 is allosterically inhibited by citrate.
e. PFK1 is allosterically inhibited by fructose 2,6-bisphosphate.

Answer 32

e. PFK1 is allosterically inhibited by fructose 2,6-bisphosphate.

Question 33

Chose the correct/right sentence regarding hepatic glycolysis.

Select one:

a. Hepatic glycolysis is activated in starvation for ATP production.
b. Hepatic glycolysis is inhibited by glucagon at two irreversible steps.
c. Hepatic glycolysis results in lactate production.
d. Hepatic glycolysis is activated when fructose 2,6-bisphosphate level decreases.
e. Hepatic glycolysis is inhibited when AMP level increases.

Answer 33

b. Hepatic glycolysis is inhibited by glucagon at two irreversible steps.

Question 34

Chose the wrong/false sentence regarding hepatic phosphofructokinase (PFK) enzymes.

Select one:

a. Hepatic glycolysis is aerobic and it is followed by conversion of pyruvate to acetyl-CoA.
b. PFK-1 becomes activated if PFK-2 is dephosphorylated.
c. Hepatic glycolysis is inhibited when citrate level increases.
d. Hepatic glycolysis is activated in starvation by fructose 2,6-bisphosphate.
e. Hepatic glycolysis is activated when AMP level increases.

Answer 34

d. Hepatic glycolysis is activated in starvation by fructose 2,6-bisphosphate.

Question 35

Chose the correct/right sentence (PDH: pyruvate dehydrogenase complex).

Select one:

a. Pyruvate activates PDH kinase and hence inhibits PDH.
b. Insulin activates PDH kinase and hence activates PDH.
c. ADP inhibits PDH kinase and hence activates PDH.
d. Ca2+ activates PDH phosphatase and hence inhibits PDH.
e. NADH activates PDH phosphatase and hence activates PDH

Answer 35

c. ADP inhibits PDH kinase and hence activates PDH.

Question 36

Chose the wrong/false sentence:

Select one:

a. Ca2+ activates PDH phosphatase and hence activates PDH.
b. NADH activates PDH phosphatase and hence activates PDH.
c. ADP inhibits PDH kinase and hence activates PDH.
d. Pyruvate inhibits PDH kinase and hence activates PDH.
e. Insulin activates PDH phosphatase and hence activates PDH.

Answer 36

b. NADH activates PDH phosphatase and hence activates PDH.

Question 37

Which enzyme contains FMN prosthetic group?

Select one:

a. E3 enzyme of PDH complex
b. Succinate dehydrogenase
c. Cytochrome c
d. Hexokinase
e. Complex I of respiratory chain

Answer 37

e. Complex I of respiratory chain

Question 38

Which compound can deliver electrons to the respiratory chain directly?

Select one:

a. Fatty acyl-CoA
b. Fumarate
c. Succinyl-CoA
d. Pyruvate
e. Oxaloacetate

Answer 38

a. Fatty acyl-CoA

Question 39

Which compound cannot deliver electrons to the respiratory chain directly?

Select one:

a. Glycerol 3-phosphate
b. NADH
c. Acetyl-CoA
d. Fatty acyl-CoA
e. Succinate

Answer 39

c. Acetyl-CoA

Question 40

Which component of the oxidative phosphorylation is localized in the inter-membrane space?

Select one:

a. Cytochrome a3
b. Ubiquinone (CoQ)
c. Fo subunit of ATP synthase
d. Cytochrome c
e. F1 subunit of ATP synthase

Answer 40

d. Cytochrome c