Chapter 24, Problem 24.19EP

(a)

Interpretation Introduction

Interpretation: To identify the name of the missing substance in the following word equation.

$\text{Glucose}+\text{ATP}\stackrel{\text{Hexokinase}}{\to }\underset{\_}{?}+\text{ADP}$

Concept introduction: Glycolysis is the metabolic pathway that breaks down a glucose molecule and converts it into two pyruvate molecules along with the production of two ATP molecules and NADH reduced coenzymes.

The block diagram to represent an overview of glycolysis is as follows:

From the above diagram, it is concluded that in the overall process of glycolysis, two stages are present.

a) Steps 1 to 3 represents a six-carbon stage $\left({\text{C}}_6\text{ stage}\right)$.

b) Steps 4 to 10 represent a three-carbon stage $\left({\text{C}}_3\text{ stage}\right)$.

The transfer of a phosphoryl group $\left({\text{PO}}_3^{2-}\right)$ is catalyzed by the kinase enzymes. In the glycolysis process, the phosphate group comes from ATP, ADP or some higher energetic phosphate molecules.

Answer to Problem 24.19EP

The complete word equation is as follows:

$\text{Glucose}+\text{ATP}\stackrel{\text{Hexokinase}}{\to }\underset{\_}{\text{Glucose 6}-\text{phosphate}}+\text{ADP}$

Explanation of Solution

The first step in the glycolysis process is the phosphorylation of glucose using ATP. Glucose is converted to $\text{glucose 6}-\text{phosphate}$. The phosphoryl group $\left({\text{PO}}_3^{2-}\right)$ is transferred from ATP to glucose, thus ATP is converted to ADP. Hexokinase enzyme catalyzes this reaction. The word equation for the phosphorylation reaction is as follows:

$\text{Glucose}+\text{ATP}\stackrel{\text{Hexokinase}}{\to }\text{Glucose 6}-\text{phosphate}+\text{ADP}$

Conclusion

In step 1, glucose is converted to $\text{glucose 6}-\text{phosphate}$. The phosphoryl group $\left({\text{PO}}_3^{2-}\right)$ is transferred from ATP to glucose. ATP is converted to ADP. Therefore, the missing substance is $\text{glucose 6}-\text{phosphate}$.

(b)

Interpretation Introduction

Interpretation: To identify the name of the missing substance in the following word equation.

$\underset{\_}{?}\stackrel{\text{Enolase}}{\rightleftharpoons }\text{Phosphoenolpyruvate}+\text{water}$

Concept introduction: Glycolysis is the metabolic pathway that breaks down a glucose molecule and converts it into two pyruvate molecules along with the production of two ATP molecules and NADH reduced coenzymes.

The block diagram to represent an overview of glycolysis is as follows:

From the above diagram, it is concluded that in the overall process of glycolysis, two stages are present.

a) Steps 1 to 3 represents a six-carbon stage $\left({\text{C}}_6\text{ stage}\right)$.

b) Steps 4 to 10 represent a three-carbon stage $\left({\text{C}}_3\text{ stage}\right)$.

Answer to Problem 24.19EP

The complete word equation is as follows:

$\underset{\_}{\text{2}-\text{Phosphoglycerate}}\stackrel{\text{Enolase}}{\rightleftharpoons }\text{Phosphoenolpyruvate}+\text{water}$

Explanation of Solution

In step 9,$\text{2}-\text{Phosphoglycerate}$ is dehydrated in the presence of enolase enzymes to give phosphoenolpyruvate. The word equation for the reaction is as follows:

$\text{2}-\text{Phosphoglycerate}\stackrel{\text{Enolase}}{\rightleftharpoons }\text{Phosphoenolpyruvate}+\text{water}$

Conclusion

In step 9,$\text{2}-\text{Phosphoglycerate}$ is dehydrated in the presence of enolase enzymes to give phosphoenolpyruvate along with water. Therefore, the missing substance is $\text{2}-\text{Phosphoglycerate}$.

(c)

Interpretation Introduction

Interpretation: To identify the name of the missing substance in the following word equation.

$3-\text{Phosphoglycerate}\stackrel{\underset{\_}{?}}{\rightleftharpoons }\text{2}-\text{Phosphoglycerate}$

Concept introduction: Glycolysis is the metabolic pathway that breaks down a glucose molecule and converts it into two pyruvate molecules along with the production of two ATP molecules and NADH reduced coenzymes.

The block diagram to represent an overview of glycolysis is as follows:

From the above diagram, it is concluded that in the overall process of glycolysis, two stages are present.

a) Steps 1 to 3 represents a six-carbon stage $\left({\text{C}}_6\text{ stage}\right)$.

b) Steps 4 to 10 represent a three-carbon stage $\left({\text{C}}_3\text{ stage}\right)$.

A mutase enzyme catalyzes the isomerization reaction by shifting a functional group from one position to another position within a molecule.

Answer to Problem 24.19EP

The complete word equation is as follows:

$3-\text{Phosphoglycerate}\stackrel{\underset{\_}{\text{Phosphoglyceromutase}}}{\rightleftharpoons }\text{2}-\text{Phosphoglycerate}$

Explanation of Solution

In step 8, $3-\text{Phosphoglycerate}$ is converted to $\text{2}-\text{Phosphoglycerate}$. Phosphoglyceromutase enzymes are involved in this reaction. The word equation for the isomerization reaction is as follows:

$3-\text{Phosphoglycerate}\stackrel{\text{Phosphoglyceromutase}}{\rightleftharpoons }\text{2}-\text{Phosphoglycerate}$

Conclusion

In step 8, $3-\text{Phosphoglycerate}$ is isomerized to $\text{2}-\text{Phosphoglycerate}$ using phosphoglyceromutase enzymes. Therefore, the missing substance is phosphoglyceromutase.

(d)

Interpretation Introduction

Interpretation: To identify the name of the substance in the following word equation.

$\text{1,3}-\text{Biphosphoglycerate}+\underset{\_}{\text{?}}\stackrel{\text{Phosphoglycerokinase}}{\rightleftharpoons }\text{3}-\text{phosphoglycerate}+\text{ATP}$

Concept introduction: Glycolysis is the metabolic pathway that breaks down a glucose molecule and converts it into two pyruvate molecules along with the production of two ATP molecules and NADH reduced coenzymes.

The block diagram to represent an overview of glycolysis is as follows:

From the above diagram, it is concluded that in the overall process of glycolysis, two stages are present.

a) Steps 1 to 3 represents a six-carbon stage $\left({\text{C}}_6\text{ stage}\right)$.

b) Steps 4 to 10 represent a three-carbon stage $\left({\text{C}}_3\text{ stage}\right)$.

The transfer of a phosphoryl group $\left({\text{PO}}_3^{2-}\right)$ is catalyzed by the kinase enzymes. In the glycolysis process, the phosphate group comes from ATP, ADP or some higher energetic phosphate molecules.

Answer to Problem 24.19EP

The complete word equation is as follows:

$\text{1,3}-\text{Biphosphoglycerate}+\underset{\_}{\text{ADP}}\stackrel{\text{Phosphoglycerokinase}}{\rightleftharpoons }\text{3}-\text{phosphoglycerate}+\text{ATP}$

Explanation of Solution

The seventh step in the glycolysis process is the phosphorylation of $\text{1,3}-\text{Biphosphoglycerate}$ using ADP, thus, ADP is converted to ATP. In step 7,$\text{1,3}-\text{biphosphoglycerate}$ is converted to $\text{3}-\text{phosphoglycerate}$ by phosphoglycerokinase. The word equation for the phosphorylation reaction is as follows:

$\text{1,3}-\text{Biphosphoglycerate}+\text{ADP}\stackrel{\text{Phosphoglycerokinase}}{\rightleftharpoons }\text{3}-\text{phosphoglycerate}+\text{ATP}$

Conclusion

In step 7, $\text{1,3}-\text{biphosphoglycerate}$ is phosphorylated by phosphoglycerokinase using ADP to give $\text{3}-\text{phosphoglycerate}$ along with ATP. Therefore, the missing substance is ADP.