Question

1) 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

2) 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.

3) 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.

5) Glucose 6-phosphate allosterically inhibits

A) hexokinase I.

B) glucokinase.

C) hexokinase II.

D) All of the above

E) A and C only

6) 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.

7) 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%

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.

9) 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.

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.

11) 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.

12) Enzymes that catalyze the same reaction are called ________.

A) isozymes

B) complementary enzymes

C) cofactors

D) catalytes

13) 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

14) 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.

15) 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.

16) 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.

17) 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.

18) 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.

19) 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.

20) 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

21) 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.

Answer 1

1) How many ATP molecules are consumed in the hexose stage of glycolysis for every one molecule of glucose?

CORRECT ANSWER - OPTION C) 2

Explanation :

In the preparatory phase or hexose stage of glycolysis, 2 ATP molecules are consumed - first to convert Glucose to Glucose - 6 phosphate and secondly to convert Fructose - 6 - phosphate to Fructose-1,6-bisphosphate.

2) During glycolysis, isomerization occurs during which of the following reactions?

CORRECT OPTION - C) Glucose 6- phosphate → fructose 6- phosphate.

Explanation :

Isomerisation of Glucose - 6 phosphate to Fructose-6-phosphate is catalysed by phosphoglucoisomerase. It is called isomerisation because the empirical formula is same but the arrangement of atoms is changed.

3) An intramolecular phosphoryl-group transfer occurs when

CORRECT ANSWER - D) None of the above.

Explanation :

Option A is incorrect since there is no phosphoryl group transfer in that reaction

Option B is incorrect . When 1,3-bisphosphoglycerate is converted to 3-phosphoglycerate., phosphoryl group is transferred to an ADP molecule. This is not intramolecular phosphoryl group transfer. It is intermolecular phosphoryl group transfer.

5) Glucose 6-phosphate allosterically inhibits

CORRECT ANSWER -E) A and C only

Explanation :

Glucose-6-phosphate allosterically inhibits Hexokinase I, II and III but cannoth inhibit glucokinase present in liver cells.

6) Glyceraldehyde 3-phosphate dehydrogenase causes

CORRECT ANSWER - A) the reduction and phosphorylation of glyceraldehyde 3-phosphate to produce 1,3-bisphosphoglycerate.

Explanation :

Option A is correct since glyceraldehyde 3-phosphate is reduced by NAD+ to form NADH and also phosphorylated by G3PD enzyme to form 1,3-bisphosphoglycerate.

Option B is incorrect since NAD+ is not oxidised but reduced.

7) 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.

CORRECT ANSWER - C) 50%

Explanation:

A 6 carbon glucose forms a 6 carbon Fructose-1,6-bisphosphate which has one phosphate atom attached to C-1 and C-3. Since Fructose-1,6-bisphosphate is cleaved to produce two 3 carbon molecules - Glyceraldehyde-3-phosphate and Dihydroxyacetone, there is a 50% chance that Glyceraldehyde-3-phosphate will have a radioactive carbon atom.

8) Which of the following enzymatic reactions are control points for glycolysis?

CORRECT ANSWER - D) Neither A nor B.

Explanation:

Neither options are correct since control points in glycolysis are conversion of Glucose to Glucose - 6 - phosphate, Fructose - 6- phosphate to Fructose - 1,6, bisphosphate and Phosphoenolpyruvate to Pyruvate.

9) Mutases are described as

CORRECT ANSWER -B) isomerases that catalyze the transfer of phosphoryl groups from one part of a substrate molecule to another.

Explanation:

Mutases are enzymes which catalyse phosphoryl group transfer inside the same molecule.

Option A is incorrect since it is partially correct and doesn't mention about intramolecular phosphoryl group transfer.

Option C is incorrect since no free Pi is released by mutases.

11) Transfer of the phosphoryl group from PEP to ADP is an example of

CORRECT ANSWER IS - D) substrate-level phosphorylation.

Explanation :

Two substrate level phosphorylations occur in Glycolysis - out of which one is conversion of PEP to Pyruvate. It is called so since the reaction involves direct transfer of phosphate atom from the substrate to ADP to form a high energy molecule i.e. ATP.

12) Enzymes that catalyze the same reaction are called ________.

CORRECT ANSWER IS A) isozymes

Explanation :

Isozymes differ in amino acid sequence but have similar catalytic sites and catalyse same reactions.

PS - Please post the rest of the questions again. TIme is not sufficient to answe all.