Chapter 23, Problem 23.34P

Interpretation Introduction

(a)

Interpretation:

The equation for the coupled reaction of 3-phosphoglycerate with ATP to form 1,3-bisphosphoglycerate and ADP should be written.

Concept Introduction:

Phosphorylation of 1,3-bisphosphoglycerate is an energetically unfavorable reaction. By coupling with the ATP hydrolysis, this reaction can be converted to a favorable state.

Answer to Problem 23.34P

  $\begin{array}{l}\text{3-phosphoglycerate}\hfill \end{array}+\text{ATP}\to \text{1,3-bisphosphoglycerate}+\text{ADP }$

Explanation of Solution

The conversion of 1,3-bisphosphatoglycerate to 3-phosphoglycerate and hydrogen phosphate can be represented as follows:

  ${\text{1,3-bisphosphoglycerate + H}}_2\text{O }\to \begin{array}{l}\text{3-phosphoglycerate}\hfill \end{array}{\text{ + HPO}}_4{}^{2-}$........(1)

Similarly, the conversion of ATP to ADP can be represented as follows:

  ${\text{ATP + H}}_2\text{O }\to {\text{ADP + HPO}}_4{}^{2-}$........(2)

To cancel the common species and to get the desired reaction, reaction (2) should be added to the reverse of reaction (1).

The coupled reaction can be represented as follows:

  $\begin{array}{l}\begin{array}{l}\text{3-phosphoglycerate}\hfill \end{array}{\text{ + HPO}}_4{}^{2-}\to {\text{1,3-bisphosphoglycerate + H}}_2\text{O }\\ {\text{ ATP + H}}_2\text{O}\to {\text{ADP + HPO}}_4{}^{2-}\\ \overline{\underset{\_}{\begin{array}{l}\text{3-phosphoglycerate}\hfill \end{array}+\text{ATP }\to \text{ 1,3-bisphosphoglycerate }+\text{ADP }}}\end{array}$

  $$

Interpretation Introduction

(b)

Interpretation:

The energy change for this coupled reaction should be calculated.

Concept Introduction:

Phosphorylation of 1,3-bisphosphoglycerate is an energetically unfavorable reaction. by coupling with the ATP hydrolysis, this reaction can be converted to a favorable state.

In the hydrolysis of ATP breaks one phosphate group, forming ADP and hydrogen phosphate, This reaction releases 7.3 kcal/mol of energy.

When the energy of a reaction is a positive value, that reaction is an endothermic reaction and it requires the energy of surrounding to complete the reaction.

When the energy of a reaction is a negative value, that reaction is exothermic, and it releases energy by acting as an energetically favorable reaction.

Answer to Problem 23.34P

- 4.5 kcal/mol

Explanation of Solution

The conversion of 1,3-bisphosphatoglycerate to 3-phosphoglycerate and hydrogen phosphate can be represented as follows:

  ${\text{1,3-bisphosphoglycerate + H}}_2\text{O }\to \begin{array}{l}\text{3-phosphoglycerate}\hfill \end{array}{\text{ + HPO}}_4{}^{2-}$........(1)

The energy for the above reaction is $\text{ - 11}\text{.8 kacal/mol}$.

Similarly, the conversion of ATP to ADP can be represented as follows:

${\text{ATP + H}}_2\text{O }\to {\text{ADP + HPO}}_4{}^{2-}$.......(2)

The energy for the above reaction is $\text{ -7}\text{.3 kcal/mol}$.

To cancel the common species and to get the desired reaction, reaction (2) should be added to the reverse of reaction (1).

The coupled reaction can be represented as follows:

  $\begin{array}{l}\begin{array}{l}\text{3-phosphoglycerate}\hfill \end{array}{\text{ + HPO}}_4{}^{2-}\to {\text{1,3-bisphosphoglycerate + H}}_2\text{O 11}\text{.8 kcal/mol}\\ {\text{ ATP + H}}_2\text{O}\to {\text{ADP + HPO}}_4{}^{2-}\text{ -7}\text{.3 kcal/mol}\\ \overline{\underset{\_}{\begin{array}{l}\text{3-phosphoglycerate}\hfill \end{array}+\text{ATP }\to \text{ 1,3-bisphosphoglycerate }+\text{ADP +4}\text{.5 kcal/mol }}}\end{array}$

Thus, the energy change for the reaction is $+4.\text{5 kcal/mol }$.

Interpretation Introduction

(c)

Interpretation:

Whether this reaction is used to synthesize ATP from ADP should be explained.

Concept Introduction:

The reaction releases 7.3 kcal/mol of energy.

When the energy of a reaction is a positive value, that reaction is an endothermic reaction and it requires the energy of surrounding to complete the reaction.

When the energy of a reaction is a negative value, that reaction is exothermic, and it releases energy by acting as an energetically favorable reaction.

Answer to Problem 23.34P

Unfavorable

Explanation of Solution

  $\begin{array}{l}{\text{ATP + H}}_2\text{O }\to {\text{ADP + HPO}}_4{}^{2-}\text{ -7}\text{.3 kcal/mol}\\ \\ {\text{1,3-bisphosphoglycerate + H}}_2\text{O }\to \begin{array}{l}\text{3-phosphoglycerate}\hfill \end{array}{\text{ + HPO}}_4{}^{2-}\text{ - 11}\text{.8 kacal/mol}\\ \\ \begin{array}{l}\text{3-phosphoglycerate}\hfill \end{array}+\text{ATP}\to \text{1,3-bisphosphoglycerate}+\text{ADP }\end{array}$

Energy = 11.8 kcal/mol − 7.3 kcal/mol = 4.5 kcal/mol

When the energy of a reaction is a positive value, that reaction is an endothermic reaction and it requires the energy of surrounding to complete the reaction.

Therefore, the reaction is unfavorable.