Question 1

Which item is a cofactor in the reaction catalyzed by glyceraldehyde 3-phosphate dehydrogenase?

Accepted Answer

NAD+ is the cofactor used by glyceraldehyde 3-phosphate dehydrogenase in the glycolysis pathway to catalyze the conversion of glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate, with the reduction of NAD+ to NADH.

Question 2

Which reaction in glycolysis utilizes a covalent enzyme intermediate?

Accepted Answer

Aldolase forms a covalent Schiff base intermediate with the substrate during the cleavage of fructose-1,6-bisphosphate into glyceraldehyde-3-phosphate and dihydroxyacetone phosphate.

Question 3

Glucose labeled with ¹⁴C in C-1 and C-6 gives rise in glycolysis to pyruvate labeled in:

Accepted Answer

E

Question 4

If glucose labeled with ¹⁴C at C-2 were metabolized in the liver, the first radioactive pyruvate formed would be labeled in:

Accepted Answer

Glucose labeled at C-2 means that the second carbon of glucose is labeled. During glycolysis, glucose is converted to pyruvate. Pyruvate is a 3-carbon compound that contains a carbonyl group (C=O) and a carboxyl group (COO-). The second carbon of glucose becomes the carbonyl carbon of pyruvate. Therefore, the first radioactive pyruvate formed would be labeled at its carbonyl carbon, which is the second carbon of glucose.

Question 5

When a mixture of glucose 6-phosphate and fructose 6-phosphate is incubated with the enzyme phosphohexose isomerase, the final mixture contains twice as much glucose 6-phosphate as fructose 6-phosphate. Which statement is MOST nearly correct, when applied to the reaction below (R = 8.315 J/mol · K and T = 298 K)? glucose 6-phosphate $\leftrightarrow$ fructose 6-phosphate

Accepted Answer

The equilibrium constant (K) for the reaction can be calculated using the ratio of products to reactants at equilibrium. Given that glucose 6-phosphate is twice as abundant as fructose 6-phosphate, the ratio is 2:1, indicating the reaction does not lie completely on one side, and thus ΔG'° cannot be zero or incalculably large. The positive ΔG'° value indicates that the reaction is not spontaneous under standard conditions, but it does not preclude the reaction from occurring in a cell where conditions are not standard.

Question 6

In glycolysis, fructose 1,6-bisphosphate is converted to two products with a standard free-energy change ($\Delta$G'°) of 23.8 kJ/mol. Under what conditions (encountered in a normal cell) will the free-energy change ($\Delta$G) be negative, enabling the reaction to proceed to the right?

Accepted Answer

The free-energy change (F1F1F1S1F1F1F10G'°) of 23.8 kJ/mol is positive, indicating that the reaction is not spontaneous and will not proceed to the right under standard conditions. However, if the concentration of fructose 1,6-bisphosphate is high relative to the concentration of products, the reaction can proceed to the right because the concentration gradient will favor the formation of products. Therefore, choice D is the best answer.

Question 7

Which reaction in glycolysis requires ATP as a substrate?

Accepted Answer

Hexokinase requires ATP as a substrate to add a phosphate group to glucose, forming glucose-6-phosphate.

Question 8

The compound [¹⁸F]2-fluoro-2-deoxyglucose is a(n):

Accepted Answer

[¹⁸F]2-fluoro-2-deoxyglucose is commonly known as FDG, which is an imaging agent used to detect tumors in PET (positron emission tomography) scans. It is taken up by tumors more readily than regular glucose and emits a signal that can be detected by the PET scanner, allowing for the detection and localization of tumor cells.

Question 9

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:

Accepted Answer

The conversion of 1 mol of fructose 1,6-bisphosphate to 2 mol of pyruvate through glycolysis results in the net formation of 2 mol of NADH (from the oxidation steps) and 4 mol of ATP (2 mol are used in the early steps of glycolysis, but 4 mol are produced in the later steps, resulting in a net gain of 2 mol ATP per glucose molecule, which equals 4 mol ATP for the 2 triose phosphates derived from each fructose 1,6-bisphosphate).

Question 10

Which reaction in glycolysis utilizes a covalent enzyme intermediate?

Accepted Answer

Glyceraldehyde-3-phosphate dehydrogenase utilizes a covalent enzyme intermediate in which an oxidation-reduction reaction takes place, leading to the formation of NADH and a high-energy phosphorylated intermediate. The other reactions in glycolysis do not involve a covalent enzyme intermediate.

Question 11

The first reaction in glycolysis that results in the formation of an energy-rich compound is catalyzed by:

Accepted Answer

Glyceraldehyde 3-phosphate dehydrogenase catalyzes the conversion of glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate, which is the first step in glycolysis that produces an energy-rich compound (in the form of a high-energy phosphate bond). This step is also coupled with the reduction of NAD+ to NADH, contributing to the energy yield of glycolysis.

Question 12

Glycogen is converted to monosaccharide units by:

Accepted Answer

Glycogen phosphorylase is the enzyme responsible for breaking down glycogen into its component glucose monomers through the process of glycogenolysis.

Question 13

Which reaction in glycolysis is a ketose to aldose isomerization?

Accepted Answer

The only reaction in glycolysis that involves an isomerization of a ketose to an aldose is the conversion of dihydroxyacetone phosphate (DHAP) to glyceraldehyde 3-phosphate (G3P) by triose phosphate isomerase.

Question 14

Which reaction in glycolysis produces ATP as a product?

Accepted Answer

Pyruvate kinase is the enzyme responsible for the final step of glycolysis, in which phosphoenolpyruvate is converted to pyruvate with the production of ATP.

Question 15

The steps of glycolysis between glyceraldehyde 3-phosphate and 3-phosphoglycerate do NOT involve:

Accepted Answer

The step between glyceraldehyde 3-phosphate and 3-phosphoglycerate involves the conversion of glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate by the enzyme glyceraldehyde 3-phosphate dehydrogenase. This step also involves the oxidation of NADH to NAD+. However, there is no formation or utilization of NADPH or P_i in this step. Additionally, ATP is synthesized in the later steps of glycolysis, but not in this specific step. Phosphoglycerate kinase catalyzes the conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate.

Question 16

In the phosphoglycerate mutase reaction, the side chain of which amino acid in the enzyme is transiently phosphorylated as part of the reaction?

Accepted Answer

Histidine is the amino acid that is transiently phosphorylated in the phosphoglycerate mutase reaction.

Question 17

Inorganic fluoride inhibits enolase. In an anaerobic system that is metabolizing glucose as a substrate, which compound would you expect to increase in concentration following the addition of fluoride?

Accepted Answer

Fluoride inhibits enolase, which converts 2-phosphoglycerate to phosphoenolpyruvate. Thus, 2-phosphoglycerate will accumulate.

Question 18

Galactosemia is a genetic error of metabolism associated with:

Accepted Answer

Galactosemia is caused by a deficiency in the enzyme UDP-glucose: galactose 1-phosphate uridylyltransferase, which leads to toxic levels of galactose 1-phosphate that can cause damage to organs and tissues. Deficiencies in galactokinase or UDP-galactose are also associated with galactosemia, but they are less common. Excessive ingestion of galactose or inability to digest lactose are not associated with galactosemia.

Question 19

Glycolysis is the name given to a metabolic pathway occurring in many different cell types. It consists of 11 enzymatic steps that convert glucose to lactic acid. Glycolysis is an example of:

Accepted Answer

Glycolysis produces lactic acid, which is a product of fermentation. Therefore, glycolysis is an example of fermentation.

Question 20

Which reaction in glycolysis is an aldose to ketose isomerization?

Accepted Answer

Phosphohexose isomerase catalyzes the conversion of glucose-6-phosphate (an aldose) to its isomer fructose-6-phosphate (a ketose).

Quiz 14: Glycolysis, Gluconeogenesis, and the Pentose Phosphate Pathway

Which item is a cofactor in the reaction catalyzed by glyceraldehyde 3-phosphate dehydrogenase?

Which reaction in glycolysis utilizes a covalent enzyme intermediate?

Glucose labeled with ¹⁴C in C-1 and C-6 gives rise in glycolysis to pyruvate labeled in:

If glucose labeled with ¹⁴C at C-2 were metabolized in the liver, the first radioactive pyruvate formed would be labeled in:

In glycolysis, fructose 1,6-bisphosphate is converted to two products with a standard free-energy change ( $\Delta$ G'°) of 23.8 kJ/mol. Under what conditions (encountered in a normal cell) will the free-energy change ( $\Delta$ G) be negative, enabling the reaction to proceed to the right?

Which reaction in glycolysis requires ATP as a substrate?

The compound [¹⁸F]2-fluoro-2-deoxyglucose is a(n) :

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:

Which reaction in glycolysis utilizes a covalent enzyme intermediate?

The first reaction in glycolysis that results in the formation of an energy-rich compound is catalyzed by:

Glycogen is converted to monosaccharide units by:

Which reaction in glycolysis is a ketose to aldose isomerization?

Which reaction in glycolysis produces ATP as a product?

The steps of glycolysis between glyceraldehyde 3-phosphate and 3-phosphoglycerate do NOT involve:

In the phosphoglycerate mutase reaction, the side chain of which amino acid in the enzyme is transiently phosphorylated as part of the reaction?

Inorganic fluoride inhibits enolase. In an anaerobic system that is metabolizing glucose as a substrate, which compound would you expect to increase in concentration following the addition of fluoride?

Galactosemia is a genetic error of metabolism associated with:

Glycolysis is the name given to a metabolic pathway occurring in many different cell types. It consists of 11 enzymatic steps that convert glucose to lactic acid. Glycolysis is an example of:

Which reaction in glycolysis is an aldose to ketose isomerization?

Quiz 14: Glycolysis, Gluconeogenesis, and the Pentose Phosphate Pathway

Which item is a cofactor in the reaction catalyzed by glyceraldehyde 3-phosphate dehydrogenase?

Which reaction in glycolysis utilizes a covalent enzyme intermediate?

Glucose labeled with 14C in C-1 and C-6 gives rise in glycolysis to pyruvate labeled in:

If glucose labeled with 14C at C-2 were metabolized in the liver, the first radioactive pyruvate formed would be labeled in:

In glycolysis, fructose 1,6-bisphosphate is converted to two products with a standard free-energy change ( Δ\DeltaΔ G'°) of 23.8 kJ/mol. Under what conditions (encountered in a normal cell) will the free-energy change ( Δ\DeltaΔ G) be negative, enabling the reaction to proceed to the right?

Which reaction in glycolysis requires ATP as a substrate?

The compound [18F]2-fluoro-2-deoxyglucose is a(n) :

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:

Which reaction in glycolysis utilizes a covalent enzyme intermediate?

The first reaction in glycolysis that results in the formation of an energy-rich compound is catalyzed by:

Glycogen is converted to monosaccharide units by:

Which reaction in glycolysis is a ketose to aldose isomerization?

Which reaction in glycolysis produces ATP as a product?

The steps of glycolysis between glyceraldehyde 3-phosphate and 3-phosphoglycerate do NOT involve:

In the phosphoglycerate mutase reaction, the side chain of which amino acid in the enzyme is transiently phosphorylated as part of the reaction?

Inorganic fluoride inhibits enolase. In an anaerobic system that is metabolizing glucose as a substrate, which compound would you expect to increase in concentration following the addition of fluoride?

Galactosemia is a genetic error of metabolism associated with:

Glycolysis is the name given to a metabolic pathway occurring in many different cell types. It consists of 11 enzymatic steps that convert glucose to lactic acid. Glycolysis is an example of:

Which reaction in glycolysis is an aldose to ketose isomerization?

Glucose labeled with ¹⁴C in C-1 and C-6 gives rise in glycolysis to pyruvate labeled in:

If glucose labeled with ¹⁴C at C-2 were metabolized in the liver, the first radioactive pyruvate formed would be labeled in:

In glycolysis, fructose 1,6-bisphosphate is converted to two products with a standard free-energy change ( $\Delta$ G'°) of 23.8 kJ/mol. Under what conditions (encountered in a normal cell) will the free-energy change ( $\Delta$ G) be negative, enabling the reaction to proceed to the right?

The compound [¹⁸F]2-fluoro-2-deoxyglucose is a(n) :