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Biochemistry (Questions) > Carbohydrate metabolism > Flashcards

Carbohydrate metabolism Flashcards

1
Q

Which statement is true?

a. The carbon atoms of glucose and fatty acids are oxidized to CO2 in the body.
b. The electrons of fuel molecules are transferred to O2 by electron carriers. c. Nutrient catabolism provides electrons for reductive biosynthesis.
d. Oxidative catabolism is driven by the high redox potential of molecular O2.
e. Fuel molecules can be oxidized by the removal of H atoms.

A

All correct

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2
Q

Which statement is true?

a. Oxidative catabolism is driven by the low redox potential of molecular O2.
b. Oxidative catabolism is driven by the high redox potential of molecular O2.
c. Nutrient catabolism provides electrons for reductive biosynthesis.
d. Fuel molecules can be oxidized by the addition of H atoms.
e. Fuel molecules can be oxidized by the removal of H atoms.

A

b. Oxidative catabolism is driven by the high redox potential of molecular O2.
c. Nutrient catabolism provides electrons for reductive biosynthesis.
e. Fuel molecules can be oxidized by the removal of H atoms.

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3
Q

Which statement is true regarding glycolysis?

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.

A

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.

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4
Q

Which statement is true regarding glycolysis?

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

A

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.

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5
Q

Which statement is false regarding glycolysis?

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

A

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).

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6
Q

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.

A

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.

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7
Q

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.

A

a. 3-Phosphoglycerate kinase,

d. Pyruvate kinase,

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8
Q

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.

A

b. phosphofructokinase,

c. hexokinase,

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9
Q

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.

A

a. AMP

c. fructose 2,6-bisphosphate

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10
Q

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.

A

b. citrate

e. acyl-CoA.

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11
Q

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.

A

All are correct

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12
Q

Put these molecules in the decreasing order of phosphoryl group transfer potential.

Select one or more:

a. ATP,
b. 1-3-bisphosphoglycerate (phosphate on carbon
c. glucose 6-phosphate,
d. phosphoenolpyruvate,
e. phosphocreatine.

A

d. phosphoenolpyruvate,
b. 1-3-bisphosphoglycerate (phosphate on carbon
e. phosphocreatine.

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13
Q

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.

A

d. regeneration of NAD+,

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14
Q

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.

A

e. phosphofructokinase 1.

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15
Q

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.

A

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

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16
Q

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.

A

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

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17
Q

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.

A

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

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18
Q

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.

A

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

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19
Q

Activity of phosphofructokinase1 is inhibited by

Select one or more:

a. ATP
b. citrate
c. fructose 2,6 bisphosphate
d. AMP

A

a. ATP

b. citrate

20
Q

Lactate dehydrogenase

Select one or more:

a. requires NAD as hydrogen acceptor
b. requires NADP as hydrogen acceptor
c. catalyzes a reversible process
d. requires molecular oxygen

A

a. requires NAD as hydrogen acceptor

c. catalyzes a reversible process

21
Q

Which enzyme catalyzes the first ATP producing step of glycolysis?

Select one:

a. phosphofructokinase 1
b. hexokinase
c. pyruvate kinase
d. phosphoglycerate mutase
e. phosphoglycerate kinase

A

e. phosphoglycerate kinase

22
Q

Which enzyme catalyzes the second ATP producing step of glycolysis?

Select one:

a. phosphofructokinase 1
b. hexokinase
c. pyruvate kinase
d. phosphoglycerate mutase
e. phosphoglycerate kinase

A

c. pyruvate kinase

23
Q

Which are the ATP producing steps of glycolysis?

Select one or more:

a. phosphofructokinase 1
b. lactate-dehydrogenase
c. pyruvate kinase
d. glyceraldehyde 3-phosphate dehydrogenase
e. phosphoglycerate kinase

A

c. pyruvate kinase

e. phosphoglycerate kinase

24
Q

Which are the ATP consuming steps of glycolysis?

Select one or more:

a. phosphofructokinase 1
b. lactate dehydrogenase
c. pyruvate kinase
d. hexokinase
e. phosphoglycerate kinase

A

a. phosphofructokinase 1

d. hexokinase

25
Q

Upon phosphorylation of phosphofructokinase 2 by protein kinase A in liver:

Select one:

a. it becomes active.
b. it becomes inactive.
c. phosphatase function is activated, kinase function is inactivated.
d. kinase function is activated, phosphatase function is inactivated.
e. phosphofructokinase 2 is not covalently regulated.

A

c. phosphatase function is activated, kinase function is inactivated.

26
Q 
Which of the following amino acids are only ketogenic? 
Select one or more:
a. Ser
b. Trp
c. Lys 
d. Pro 
e. Leu
A

c. Lys

e. Leu

26
Q 
Which of the following amino acids are only ketogenic? 
Select one or more:
a. Ser
b. Trp
c. Lys 
d. Pro 
e. Leu
A

c. Lys

e. Leu

27
Q

Which enzyme deficiency may result in lactic acidosis?

Select one or more:

a. Pyruvate kinase
b. Pyruvate dehydrogenase
c. Pyruvate carboxylase
d. Lactate dehydrogenase

A

b. Pyruvate dehydrogenase (acetyl CoA)

c. Pyruvate carboxylase (Oxaloacetate)

28
Q

Which condition is not found in pyrvate carboxylase deficiency?

Select one:

a. Demyelination
b. Hyperammonemia
c. Hyperglycemia
d. Hypoglycemia
e. Lactic acidosis

A

c. Hyperglycemia

29
Q

Which statements are true for hereditary fructose intolerance?

Select one or more:

a. It is caused by the inadequate function of aldolase B
b. It is accompanied by hypoglycemia
c. It results in liver damage
d. Glycogenolysis is increased
e. It results in the accumulation of fructose 1-phosphate

A

a. It is caused by the inadequate function of aldolase B
b. It is accompanied by hypoglycemia
c. It results in liver damage
e. It results in the accumulation of fructose 1-phosphate

30
Q

The allosteric activator of pyruvate carboxylase is:

Select one:

a. oxaloacetate
b. NADH
c. CoA
d. ATP
e. acetyl-coA

A

acetyl-coA

31
Q

Lactose can be formed in a single step from:

Select one or more:

a. glucose
b. UDP-galactose
c. glucosamin 6-phosphate
d. glucosamin 1-phosphate
e. glucose 1-phosphate

A

a. glucose

b. UDP-galactose

32
Q

Hypoglycemia develops when:

Select one:

a. glucagon secretion increases
b. glucokinase is defective
c. epinephrine level rises
d. insulin level is low.
e. there is an overproduction of insulin.

A

e. there is an overproduction of insulin.

33
Q

Choose the enzyme, the lack of which leads to fructose intolerance
Select one:
a. aldolase A (fructose 1,6-bisphosphate aldolase)
b. aldolase B (fructose 1-phosphate aldolase)
c. fructokinase
d. hexokinase
e. phosphofructokinase

A

b. aldolase B (fructose 1-phosphate aldolase)

34
Q

Glycolysis in the erythrocyte produces pyruvate that is further metabolized to:

Select one:

a. CO2.
b. lactate.
c. glucose.
d. hemoglobin.
e. ethanol.

A

b. lactate.

35
Q

Glycolysis in the erythrocyte produces pyruvate that is further metabolized to

Select one:

a. CO2.
b. lactate.
c. glucose.
d. hemoglobin.
e. ethanol.

A

b. lactate.

36
Q

The first reaction in glycolysis that results in the formation of an energy-rich compound (i.e., a compound whose hydrolysis has a highly negative DG’°) is catalyzed by:

Select one:

a. glyceraldehyde 3-phosphate dehydrogenase.
b. hexokinase.
c. phosphofructokinase-1.
d. phosphoglycerate kinase.
e. triose phosphate isomerase.

A

a. glyceraldehyde 3-phosphate dehydrogenase.

37
Q

The conversion of 1 mol of fructose 1,6-bisphosphate to 2 mol of pyruvate by the glycolytic pathway results in a net formation of:

Select one:

a. 2 mol of NADH and 4 mol of ATP.
b. 2 mol of NADH and 2 mol of ATP.
c. 2 mol of NAD+ and 4 mol of ATP.
d. 1 mol of NADH and 1 mol of ATP.
e. 1 mol of NAD+ and 2 mol of ATP.

A

a. 2 mol of NADH and 4 mol of ATP.

38
Q

The anaerobic conversion of 1 mol of glucose to 2 mol of lactate is accompanied by a net gain of:

Select one:

a. 1 mol of ATP.
b. 1 mol of NADH.
c. 2 mol of ATP.
d. 2 mol of NADH.

A

c. 2 mol of ATP.

39
Q

Which of these cofactors participates directly in the oxidation-reduction reactions in the conversion of glucose to lactate?

Select one:

a. FAD/FADH2
b. NAD+/NADH
c. glyceraldehyde 3-phosphate
d. ATP
e. ADP

A

b. NAD+/NADH

40
Q

Classic galactosemia is a genetic error of metabolism associated with:

Select one:

a. excessive ingestion of galactose.
b. inability to digest lactose.
c. deficiency of galactokinase.
d. deficiency of galactose 1-phosphate uridylyltransferase.
e. deficiency of UDP-glucose.

A

d. deficiency of galactose 1-phosphate uridylyltransferase.

41
Q

The rate-limiting reaction in glycolysis is:

Select one:

a. the phosphorylation of glucose.
b. the phosphorylation of fructose 6-phosphate.
c. the isomerization of glucose 6-phosphate to fructose 6-phosphate.
d. the breakdown of glycogen.
e. some step in the conversion of fructose 1,6-bisphosphate to pyruvate.

A

b. the phosphorylation of fructose 6-phosphate.

42
Q

Glucokinase:

Select one:

a. is found in all mammalian tissues.
b. is a hexokinase isozyme found in liver hepatocytes and ß-cells.
c. converts glucose 6-phosphate to fructose 6-phosphate.
d. acts in the conversion of liver glycogen to glucose 1-phosphate.

A

b. is a hexokinase isozyme found in liver hepatocytes and ß-cells.

43
Q

Identify enzyme A & B

A

A: Glyceraldehyde 3-phosphatedehydrogenase

B: Bisphosphoglycerate mutase

44
Q

Identify substrate A, B, C, D

A

A: Glyceraldehyde 3- phosphate
B: 1,3-Bisphosphoglycerate
C: 3-phosphoglycerate
D: 2,3-Bisphosphoglycerate

Biochemistry (Questions) (35 decks)

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