Deck 11: Glycolysis

Question 1

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

Answer 1

competes with phosphate for its binding site in glyceraldehyde 3-phosphate dehydrogenase.

Question 2

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

Answer 2

Both A and B

Question 3

Glucose 6-phosphate allosterically inhibits

A) hexokinase I.
B) glucokinase.
C) hexokinase II.
D) All of the above
E) A and C only

Answer 3

A and C only

Question 4

In some diabetic patients, glucose increases disproportionately and is unresponsive to an insulin challenge; under these conditions, how would oneʹs liver normally respond?

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

Question 5

Which amino acidʹs residue plays a role in the phosphoglycerate mutase reaction in glycolysis for muscle and yeast?

A) leucine
B) lysine
C) alanine
D) histidine

Question 6

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.

Question 7

Which of the following elements is required for the enzymatic reaction that produces phosphoenolpyruvate?

A) potassium
B) calcium
C) magnesium
D) manganese

Question 8

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

Question 9

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

Question 10

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

Question 11

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

Question 12

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

Question 13

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

Question 14

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.

Question 15

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

Question 16

How many ATP molecules are consumed in glycolysis for every one molecule of glucose?

A) 0; ATP is produced, not consumed, by glycolysis
B) 1
C) 2
D) 3
E) 4

Question 17

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

Question 18

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

Question 19

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

Question 20

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

Question 21

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.

Question 22

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

Question 23

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

Question 24

Which substance causes muscles to ache during strenuous exercise?

A) pyruvic acid
B) lactose dehydrogenase
C) lactate ion
D) lactic acid

Question 25

Enzymes that catalyze the same reaction are called .

A) isozymes
B) complementary enzymes
C) cofactors
D) catalytes

Question 26

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 equilmolar amounts.

Question 27

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

Question 28

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

Question 29

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

Question 30

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 Chatelierʹs 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.

Question 31

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.

Question 32

Which of the following is not regulated in glycolysis?

A) pyruvate kinase
B) phosphoglycerate kinase
C) hexokinase
D) PFK-1

Question 33

The overall △G for glycolysis is -72 kJ/mol in erythrocytes. Which statement below is true?

A) The value of △G⁰ʹ 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

Question 34

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.

Question 35

What chemical species activates the GLUT4 protein to transport glucose into cells?

A) adrenaline
B) insulin
C) protein kinase A
D) PFK-2

Question 36

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

Question 37

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

Question 38

The enzyme that catalyzes the conversion of pyruvate to lactate is .

A) lactate reductase
B) pyruvate kinase
C) lactoenolpyruvate
D) lactate dehydrogenase

Question 39

There are four enzymes that can catalyze the first step of glycolysis. They are hexokinases I, II and III and glucokinase hexokinase IV). Hexokinases I, II and III have K_m values near 0.1 mM. Glucokinase has a K_m range of 2-5 mM. If after a heavy meal the blood glucose level rises to 8 mM which statement will be true?

A) At this high blood glucose level all four hexokinases are saturated with substrate.
B) Hexokinases I, II and III are catalyzing at their maximum rate, but glucokinase can still respond to increases in blood glucose levels.
C) None of the enzymes is saturated. All of them help to increase the rate of glycolysis.
D) The flux through glucokinase will be extremely low. The only significant catalysis is done by hexokinases I, II and III.

Question 40

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? 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.

Question 41

Isozymes are different proteins from one species which catalyze different chemical reactions.

Question 42

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.

Question 43

Two molecules of ATP are consumed per glucose molecule during the hexose stage of glycolysis.

Question 44

Four molecules of ATP are consumed per glucose during the hexose stage of glycolysis.

Question 45

The slowing of glycolysis in the presence of oxygen is called the effect.

A) Bohr
B) Michaelis-Menton
C) Pastuer
D) Pauling

Question 46

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.

Question 47

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

Question 48

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

Question 49

Two molecules of ATP are produced per glucose during the hexose stage of glycolysis.

Question 50

Two molecules of ATP are consumed per glucose during the triose stage of glycolysis.

Question 51

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

Question 52

In glycolysis, there is a net yield of two molecules of ATP per molecule of glucose.

Question 53

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 ATPʹs
C) fructose produces one more ATP than glucose
D) fructose produces twice the number of ATP compared to glucose

Question 54

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. Itʹs 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.

Question 55

Which applies to fructose 1,6-bisphosphate?

A) inhibitor of pyruvate kinase
B) product of PFK-1 catalyzed step in glycolysis
C) isomer of glucose 1,6-bisphosphate
D) All of the above

Question 56

Glycolysis occurs in the cytosol of eukaryotes.

Question 57

PFK-2 and fructose 2,6-bisphosphatase are two names for the same enzyme. The name PFK-2 is used for the enzymeʹs 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.

Question 58

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 ATPʹs 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.

Question 59

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.

Question 60

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

Question 61

Under aerobic conditions yeast cells convert pyruvate to ethanol and carbon dioxide.

Question 62

Glucose is the only monosaccharide that can enter the glycolytic pathway at the first step. All other monosaccharides enter at a subsequent step in the pathway.

Question 63

Citrate is an intermediate in the citric acid cycle, yet it is also an inhibitor of PFK-1. This is an example of feedback inhibition.

Question 64

An increase in blood insulin concentration increases the rate of glucose uptake in adipose tissue and striated muscle cells.

Question 65

Glyceraldehyde 3-phosphate and dihydroxyacetone phosphate are substrates in an oxidation and phosphorylation reaction, which yields a high energy mixed anhydride.

Question 66

Glucagon triggers the adenylate cyclase signally pathway. This activates protein kinase A which phosphorylates serine residues.

Question 67

Mammals can convert pyruvate to either ethanol or lactate depending on the availability of oxygen.

Question 68

Glucagon is a pancreatic hormone that is produced in response to low blood sugar levels. At high glucagon concentrations glycolysis is slowed.

Question 69

Triose phosphate isomerase is diffusion controlled.

Question 70

Glucose is the only hexose which can enter the glycolytic pathway.

Question 71

The reaction catalyzed by PFK-1 is metabolically reversible.

Question 72

All ten steps of the glycolytic pathway must have negative free energies for glycolysis to proceed.

Question 73

Lactic acid produced by certain bacteria is used to curdle milk during cheese-making.

Question 74

Glucose is normally transported into cells by an active transport protein since the concentration of glucose inside cells is normally higher than that in the blood.