Which substance is a product of glycolysis, a precursor of gluconeogenesis and a precursor of the citric acid cycle?
A) Glucose.
B) Pyruvate.
C) ATP.
D) Coenzyme A

B

How many ATP molecules are consumed in the hexose stage of glycolysis for every one molecule of glucose?
A) 0; ATP is produced, not consumed, by glycolysis.
B) 1
C) 2
D) 3
E) 4

C

The net energy gain in glycolysis is due to the production of
A) phosphoenolpyruvate.
B) NAD.
C) NADH.
D) ADP.

C

During glycolysis, isomerization occurs during which of the following reactions?
A) Fructose 1,6-bisphosphate → dihydroxyacetone phosphate and glyceraldehyde 3-phosphate.
B) Fructose 6-phosphate → fructose 1,6-bisphosphate.
C) Glucose 6- phosphate → fructose 6- phosphate.
D) Glucose → glucose 6- phosphate

C

Transfer of a high-energy phosphoryl group to ADP, resulting in ATP occurs when
A) 1,3-bisphosphoglycerate → 3-phosphoglycerate.
B) phosphoenolpyruvate (PEP) → pyruvate.
C) 3-phosphoglycerate → 2-phosphoglycerate.
D) Both A and B.
E) None of the above.

D

An intramolecular phosphoryl-group transfer occurs when
A) 2-phosphoglycerate is converted to phosphoenolpyruvate.
B) 1,3-bisphosphoglycerate is converted to 3-phosphoglycerate.
C) Both A and B.
D) None of the above

D

How would the liver normally respond under condition of high glucose?
A) Phosphorylating glucose for entry into the glycolytic pathway.
B) Saturating glucokinase with glucose.
C) Phosphorylating glucose for entry into the glycogen synthesis pathways.
D) A and B only.
E) A and C only

E

Glucose 6-phosphate allosterically inhibits
A) hexokinase I.
B) glucokinase.
C) hexokinase II.
D) All of the above
E) A and C only

E

Isozymes are enzymes
A) from one species that catalyze the same reaction.
B) from different species that catalyze the same reaction.
C) that have isomers as substrates.
D) that have products that are isomers.

A

Phosphofructokinase I deficiency results in
A) an overproduction of Fructose 6-phosphate.
B) an overproduction of Fructose 1,6-bisphosphate.
C) fructose 1,6-bisphosphate deficiency.
D) A and C only.
E) All of the above

D

Glyceraldehyde 3-phosphate dehydrogenase causes
A) the reduction and phosphorylation of glyceraldehyde 3-phosphate to produce 1,3-bisphosphoglycerate.
B) the oxidation of a molecule of NAD+ to NADH.
C) Neither A nor B.
D) Both A and B

C

The glucose 6-phospate isomerase reaction is a near-equilibrium reaction. Therefore, at any time in a cell there is
A) little or no glucose- 6-phospate remaining.
B) about equal amounts of glucose- 6-phosphate and fructose -6-phospate.
C) an accumulation of fructose 6-phosphate.
D) All of the above.

B

A cell that has been fed glucose containing carbon — radioactive with carbon 14 in carbon #1 will have ________ percent of the radioactivity in each mole of glyceraldehyde-3-phosphate.
A) 0%
B) 25%
C) 50%
D) 100%

C

Although the Gibbs free energy change for the reaction of triose phosphate isomerase is positive (+6.7 kj/mole), the reaction product (1, 3-bisphosphoglycerate) is reduced to zero because
A) triose phosphate isomerase is written left to right.
B) triosephosphate isomerase is complexed to phosphoglycerate kinase, the next step in the sequence of reactions.
C) there are too few molecules of dihydroxyacetone phosphate available.
D) there are allosteric stimulants of triose phosphate isomerase.

B

2,3-bisphosphoglycerate is
A) an essential component of glycolysis for ATP production.
B) converted to 3-phosphoglycerate with formation of ATP.
C) essential for the efficient release of O2 from hemoglobin.
D) a product of the enzyme phosphofructokinase.

C

Which of the following enzymatic reactions are control points for glycolysis?
A) Glucose 6-phosphate isomerase.
B) Aldolase.
C) Both A and B.
D) Neither A nor B

D

Arsenate
A) competes with NAD+ for the binding site in 1,3-bisphosphoglycerate.
B) competes with phosphate for its binding site in glyceraldehyde 3-phosphate dehydrogenase.
C) produces a stable analog of 1,3-bisphosphoglycerate.
D) All of the above.

B

In the presence of arsenate poisoning
A) ATP production proceeds via a reaction that involves 1,3-bisphosphoglycerate.
B) glycolysis is interrupted.
C) a net production of 2 molecules of ATP occurs.
D) All of the above.
E) None of the above

E

Arsenite
A) poisons by the same mechanism as arsenate.
B) is less toxic than arsenate.
C) binds tightly to lipoamide sulfur atoms.
D) None of the above

C

Substrate level phosphorylation
A) describes the conversion of ADP into ATP with the addition of inorganic phosphate every place throughout the cell.
B) describes the formation of ADP by phosphoryl group transfer from 1,3 bisphosphoglycerate.
C) is the formation of ATP by phosphoryl group transfer from a higher energy compound.
D) Both A and C.

C

Mutases are described as
A) polymerases that catalyze phosphoryl group transfers.
B) isomerases that catalyze the transfer of phosphoryl groups from one part of a substrate molecule to another.
C) forming intermediate free phosphate (Pi).
D) All of the above.

B

Which amino acid's residue plays a role in the phosphoglycerate mutase reaction in glycolysis for muscle and yeast?
A) Leucine.
B) Lysine.
C) Alanine.
D) Histidine

D

Which of the following mutases catalyze the formation of a 2,3-BPG intermediate?
A) Muscle phosphoglycerate mutases.
B) Plant phosphoglycerate mutases.
C) Yeast phosphoglycerate mutases.
D) A and C only.
E) All of the above

D

Which of the following elements is required for the enzymatic reaction that produces phosphoenolpyruvate?
A) Potassium.
B) Calcium.
C) Magnesium.
D) Manganese

C

Which of the following is not regulated in glycolysis?
A) Pyruvate kinase.
B) Phosphoglycerate kinase.
C) Hexokinase.
D) PFK-1.

B

Transfer of the phosphoryl group from PEP to ADP is an example of
A) a mutase reaction.
B) isomerization.
C) dehydrogenase.
D) substrate-level phosphorylation

D

Which of the following is not a metabolically irreversible enzymatic reaction of glycolysis?
A) Pyruvate kinase reaction.
B) PFK-1 reaction.
C) Hexokinase/Glucokinase reaction.
D) None of the above

D

Enzymes that catalyze the same reaction are called ________.
A) isozymes
B) complementary enzymes
C) cofactors
D) catalytes

A

Cells that form ATP mainly by glycolysis are
A) anaerobic yeasts.
B) lactic acid bacteria.
C) kidney medulla cells.
D) A and B.
E) A, B and C

E

The conversion of pyruvate to ethanol also causes the ________.
A) oxidation of NADH
B) production of ADP
C) consumption of O2
D) generation of an ion gradient across mitochondrial membranes

A

Yeast will normally convert pyruvate to ethanol. Why is this better for the yeast than a conversion to lactate?
A) Conversion to ethanol releases more NAD+ per mole than the conversion to lactate.
B) The carbon atoms are more oxidized in ethanol than in lactate.
C) Ethanol is neutral, but lactate production is accompanied by a sharp decrease in pH.
D) Ethanol production is not better. Yeast normally produces ethanol and lactate in equimolar amounts.

C

Compared to pyruvate, the carbon atoms in lactate ________.
A) are more reduced
B) are more oxidized
C) are equally as oxidized
D) carry more charge

A

The enzyme that catalyzes the conversion of pyruvate to lactate is ________.
A) lactate reductase
B) pyruvate kinase
C) lactoenolpyruvate
D) lactate dehydrogenase

D

Which is among the possible fates of pyruvate after glycolysis?
A) Conversion to lactate.
B) Further reduction by the citric acid cycle.
C) Conversion to ethanol.
D) All of the above

D

Pyruvate can be converted to the amino acid ________ in all species.
A) lysine
B) glycine
C) alanine
D) all of the above

C

Fermentation is a process where electrons from glycolysis — in the form of NADH — are passed to
A) the membrane associated electron transport chain.
B) only ethanol.
C) ethanol and other organic compounds.
D) oxygen.

C

What happens to pyruvate if it is destined for the citric acid cycle?
A) It is converted to carbon dioxide and acetaldehyde.
B) It is converted to ethanol.
C) It is converted to lactate.
D) Nothing, pyruvate enters the citric acid cycle directly

A

Under what situation might lactic acidosis occur?
A) Lactate dehydrogenase is inactive.
B) Transport of glucose into cells is accelerated.
C) Oxygen supply to tissues is inadequate.
D) PFK-1 is over-activated.

C

Hamsters love to run on exercise wheels. Prolonged running at a high rate of speed requires ATP. Could a hamster with a defective gene for the enzyme lactate dehydrogenase meet the extra ATP demand for prolonged, fast wheel-running by maintaining a high rate of glycolysis when muscles are operating under anaerobic conditions? Why or why not?
A) No, not enough NAD+ can be regenerated for glycolysis to continue at a high rate.
B) No, the defective gene will cause a rapid decline in pH in the muscles used for running.
C) Yes, the defective enzyme has no effect on the glycolytic pathway.
D) Yes, the enzyme alcohol dehydrogenase will supply the needed NAD+ if the lactose dehydrogenase cannot

A

Which substance causes muscles to ache during strenuous exercise?
A) Pyruvic acid.
B) Lactose dehydrogenase.
C) Lactate ion.
D) Lactic acid

D

Seven of the ten reactions in the glycolytic pathway have free energy values close to zero. What does this tell us about those reactions?
A) They are near equilibrium reactions.
B) They are not control points for pathway regulation.
C) They are reversible reactions.
D) All of the above.
E) None of the above

D

The overall △G for glycolysis is -72 kJ/mol in erythrocytes. Which statement below is true?
A) The value of △G0' is also -72 kJ/mol since the cytosol pH is close to 7.
B) The free energy of glycolysis is found as the sum of the standard free energy changes for the individual pathway reactions.
C) The negative sign of △G shows that this pathway will proceed toward product (pyruvate) under normal cellular conditions.
D) All of the above.

C

Some reaction steps in the glycolytic pathway have positive standard free energy changes. Which statements apply?
A) The standard free energy for these steps is not the same as the actual free energy change in cells. The actual free energy change must be negative or zero.
B) The reaction steps with positive standard free energy changes are likely to be regulatory steps for the pathway.
C) The steps with a positive standard free energy change are the fastest steps in the pathway.
D) The steps with a positive standard free energy change must be coupled to an ATP →ADP conversion.

A

Which must be satisfied to obtain net flux toward product in a metabolic pathway?
A) Each step in the pathway has an actual free energy change that is either negative or zero.
B) The overall actual free energy change is negative.
C) The net enthalpy is endothermic.
D) A and B above.
E) All of the above.

D

What chemical species activates the GLUT4 protein to transport glucose into cells?
A) Adrenaline.
B) Insulin.
C) Protein kinase A.
D) PFK-2.

B

Once inside a cell, glucose is rapidly phosphorylated to glucose-6-phosphate. What is the main purpose of this phosphorylation?
A) To keep glucose inside the cell.
B) To form a high-energy compound.
C) To activate PFK-1.
D) To prevent mutarotation

A

The activity of which glycolytic enzyme shown below is not used to control the rate of glycolysis?
A) PFK-1.
B) Pyruvate kinase.
C) Triose phosphate isomerase.
D) Hexokinase

C

The activity of which glycolytic enzyme shown below is not used to control the rate of glycolysis?
A) PFK-1.
B) Pyruvate kinase.
C) Triose phosphate isomerase.
D) Hexokinase

B

ATP is a cosubstrate of the enzyme PFK-1. In most species ATP is also an inhibitor of PFK-1 at higher concentrations. This seems to violate Le Chatelier's Principle. Which statement below would provide a suitable explanation?
A) PFK-1 must be phosphorylated by ATP in the active site and the phosphorylated PFK-1 must be the less active form.
B) There must be another cofactor interacting with ATP at high concentrations to achieve inhibition of PFK-1.
C) ATP actually activates the reverse of the reaction preceding the PFK-1 step in the pathway. It likely has no direct effect on PFK-1.
D) There are two sites on PFK-1 that bind ATP. One is the active site; the other is the regulatory site where inhibition occurs

D

Insulin increases the capacity of a cell to transport glucose by
A) forming more GLUT 4 vesicles.
B) stimulating hexokinase.
C) stimulating GLUTs 1, 3 and others of the GLUT family.
D) stimulating GLUT 4 vesicles to fuse with the plasma membrane

D

More than one step in the glycolytic pathway is subject to regulation. It might seem most efficient to regulate only the first step of a pathway to avoid buildup of intermediates and to conserve materials and energy. Why is the first step of glycolysis not the only regulated step?
A) Some sugars can enter the glycolytic pathway beyond the first step. If steps other than step one were not regulated, the breakdown of these sugars would be essentially uncontrolled.
B) Having more than one regulated step in the pathway allows for feedback inhibition.
C) Control of a single step in a reaction pathway is difficult because the concentrations of enzymes in cells are very low. It's easier to control more than one enzyme.
D) All the ATP in a cell would be depleted very quickly if only the first step of glycolysis were regulated.

A

In strenuously working muscle the pH decreases. This inhibits the activity of PFK-1 and glycolysis slows. Why would it be desirable to slow glycolysis when the demand for ATP is high?
A) Inhibition of PFK-1 allows for the complete oxidation of pyruvate via the citric acid cycle.
B) Slowing glycolysis slows the rate of decrease in pH. A low pH can be harmful and potentially fatal.
C) The less active form of PFK-1 is a potent allosteric activator of creatine, so even though glycolysis is slowed, ATP production is actually increased by the activation of creatine.
D) As PFK-1 is inhibited, its isozyme, PFK-2 is activated. PFK-2 is functional at a much lower pH than PFK-1.

B

PFK-2 and fructose 2,6-bisphosphatase are two names for the same enzyme. The name PFK-2 is used for the enzyme's catalysis of the phosphorylation of fructose 6-phosphate to fructose 2,6-bisphosphate. The name fructose 2,6-bisphosphatase is used for its catalysis of the reverse reaction. What is unique about this enzyme that makes it logical to use two names?
A) It is one of very few enzymes that can catalyze both the forward and reverse reactions.
B) The enzyme is a monomer when catalyzing the phosphorylation reaction and a dimer when catalyzing the reverse reaction.
C) The forward and reverse reactions occur in different compartments within the cell, so a different name is used for each activity.
D) The enzyme is bifunctional. The forward and reverse reactions are catalyzed by different sites on the same enzyme.

D

Which applies to fructose 1,6-bisphosphate?
A) Activator of pyruvate kinase.
B) Product of PFK-1 catalyzed step in glycolysis.
C) Isomer of glucose 1,6-bisphosphate.
D) All of the above

D

The slowing of glycolysis in the presence of oxygen is called the ________ effect.
A) Bohr
B) Michaelis-Menton
C) Pasteur
D) Pauling

C

What are the effects of protein kinase A on PFK-2 and pyruvate kinase?
A) Phosphorylates PFK-2; dephosphorylated pyruvate kinase; both enzymes are inhibited.
B) Phosphorylates both enzymes; inhibits both enzymes.
C) Dephosphorylates both enzymes; inhibits both enzymes.
D) Dephosphorylates PFK-2; phosphorylates pyruvate kinase; activates PFK-2; inhibits pyruvate kinase.

B

In the liver, ________ has a main use for maintaining blood glucose, but it can also be used to synthesize glycogen, or enter the pentose phosphate pathway to produce ribose 5-phosphate.
A) glucose-1-phosphate
B) glucose-1,6-bisphosphate
C) fructose-6-phosphate
D) glucose-6-phosphate

D

A patient is found to be deficient in the enzyme galactose 1-phosphate uridylyltransferase. Specifically due to this deficiency what might a doctor recommend?
A) Avoid all strenuous exercise.
B) Eat a fat-free diet.
C) Increase intake of vitamin C.
D) Avoid ingestion of milk and milk products.

D

How does the number of molecules of ATP produced compare for conversion of one molecule of either glucose or fructose to pyruvate?
A) Fructose produces one less ATP than glucose.
B) Fructose and glucose produce the same number of ATPs.
C) Fructose produces one more ATP than glucose.
D) Fructose produces twice the number of ATP compared to glucose

B

The molecule 1,3-bisphosphoglycerate can be converted to 3-phosphoenolpyruvate two ways. One way is catalyzed by the glycolytic pathway enzyme phosphoglycerate kinase. The other route is a two step reaction sequence that uses the enzymes bisphosphoglycerate mutase and 2,3-bisphosphoglycerate phosphatase. The intermediate product of the two-step sequence is 2,3-BPG which is an allosteric inhibitor of hemoglobin. What disadvantage would there be if the glycolytic pathway only used the two-step reaction sequence?
A) The step catalyzed by phosphoglycerate kinase is one of the ATP producing steps of glycolysis. Using only the two-step reaction sequence would reduce the number of ATP's produced.
B) There is no disadvantage to the two-step sequence other than having to use more than one enzyme.
C) The molecule 2,3-BPG is also a potent inhibitor of PFK-1. Even transient production of 2,3-BPG will significantly slow glycolysis.
D) Too much 2,3-BPG would be produced which would cause clumping of red blood cells.

A

How does mannose enter the glycolytic pathway?
A) It is converted mannose 6-phosphate and then isomerized to fructose 6-phosphate which enters the pathway.
B) It can enter directly into the first step of glycolysis because hexokinase converts mannose to glucose 6-phosphate.
C) Mannose is first split into two trioses that are directly converted to glyceraldehyde 3-phosphate.
D) Mannose is not metabolized via glycolysis. It enters a separate pathway.

A

What is the function of the enzyme invertase?
A) It cleaves lactose into galactose and glucose.
B) It converts glucose into fructose.
C) It interconverts glucose between its R and S enantiomers.
D) It cleaves sucrose into glucose and fructose

D

The genetic disorder galactosemia can cause ________ in infants.
A) inability to properly digest milk due to its galactose content
B) jaundice
C) damage to the nervous system
D) liver damage
E) All of the above

E

Which statement is false about the Entner-Doudoroff pathway?
A) It produces less ATP per glucose molecule than glycolysis.
B) Organisms that have this pathway use it only under conditions of low glyceraldehyde 3-phosphate isomerase concentrations.
C) It is useful for bacteria that do not have PFK-1.
D) The pathway produces pyruvate and glyceraldehyde 3-phosphate.
E) It enables some bacteria to survive on gluconate and other organic acids that cannot be metabolized via glycolysis.

B

Which is not part of the Entner-Doudoroff pathway?
A) Consumption of ATP.
B) The enzyme gluconolactonase.
C) An unusual dehydrase reaction from 6-phosphogluconate to KDPG.
D) The production of pyruvate.
E) The production of NADPH

A

Which will be the main energy-producing degradation pathway for E. coli being grown on a medium where gluconate is the only carbon source?
A) Embden-Meyeroff-Parnas.
B) Entner-Doudoroff.
C) Pentose phosphate.
D) Gycolytic.

B