Chapter 18, Problem 1P

Characterizing Glycolysis List the reactions of glycolysis that

a. are energy consuming (under standard-stale conditions),

b. are energy yielding (under standard-state conditions),

c. consume ATP.

d. yield ATP

e. are strongly influenced by changes in concentration of substrate and product because of their molecularity.

f. are at or near equilibrium in the erythrocyte (see Table 18.2).

Interpretation Introduction

(a)

To write: The reaction of glycolysis which are energy consuming under standard-state conditions.

Introduction: Glycolysis is a series of chemical reaction in the body which synthesizes energy in the form of ATP by breaking down glucose molecules. Glycolysis is an extramitochondrial chemical reaction and takes place in the cytoplasm to produce energy in the form of ATP.

Reactions that consume energy to complete would have a positive value of $\Delta G$ and also a positive standard state free energy of the reaction $\Delta G^{°\text{'}}$ . While a reaction that releases energy would have a negative value for both the energies $\Delta G$ and $\Delta G^{°\text{'}}$ .

Explanation of Solution

The first step of Glycolysis is energy-consuming in nature.

The following reactions of glycolysis are energy consuming reactions:

  $\begin{array}{l}\text{Glucose-6-phosphate}\stackrel{\text{Phosphoglucoisomerase}}{\rightleftarrows }\text{Fructose-6-phosphate}\\ \text{Fructose-1,6-biphosphate}\stackrel{\text{Fructosebiphosphat ealdose}}{\rightleftarrows }\text{Dihydroxyacetone-P + Glyceraldehyde-3-P}\\ \text{Dihydroxyacetone-P}\stackrel{\text{Triosephosphate isomerase}}{\rightleftarrows }\text{Glyceraldehyde-3-P}\\ {\text{Glyceraldehyde-3-P+NAD}}^{\text{+}}{\text{+P}}_{\text{i}}\stackrel{\text{Glyceraldehyde-3-Pdehydrogenase}}{\rightleftarrows }{\text{1,3-Biphosphoglycerate + NADH + H}}^{\text{+}}\\ \text{3-Phosphoglycerate}\stackrel{\text{Phosphoglycerate mutase}}{\rightleftarrows }\text{2-Phosphoglycerate}\\ \text{2-Phosphoglycerate}\stackrel{\text{Enolase}}{\rightleftarrows }{\text{Phosphoenolpyruvate + H}}_{\text{2}}\text{O}\end{array}$

Thus, the above reaction consumes energy and has positive value for both energies of the reaction.

Interpretation Introduction

To write: The reaction of glycolysis which are energy releasing under standard-state conditions.

Introduction: Glycolysis is a series of chemical reaction in the body which synthesizes energy in the form of ATP by breaking down glucose molecules. Glycolysis is an extramitochondrial chemical reaction and takes place in the cytoplasm to produce energy in the form of ATP.

Reactions that consume energy to complete would have a positive value of $\Delta G$ and also a positive standard state free energy of the reaction $\Delta G^{°\text{'}}$ . While a reaction that releases energy would have a negative value for both the energies $\Delta G$ and $\Delta G^{°\text{'}}$ .

Explanation of Solution

The following reactions of glycolysis are energy-releasing reactions:

  $\begin{array}{l}\text{Glucose + ATP}\stackrel{\text{Hexokinase}}{\rightleftarrows }\text{Glucose-6-phosphate + ADP}\\ \text{Fructose-6-phosphate + ATP}\stackrel{\text{Phosphofructokinase}}{\rightleftarrows }\text{Fructose-1,6-biphosphate + ADP}\\ \text{1,3-Biphosphoglycerate + ADP}\stackrel{\text{Phosphoglyceratekinase}}{\rightleftarrows }\text{3-P-Glycerate + ATP}\\ \text{Phosphoenolpyruvate + ADP}\stackrel{\text{Pyruvatekinase}}{\rightleftarrows }\text{Pyruvate + ATP}\\ \text{Pyruvate + NADH}\stackrel{\text{LactateDehydrogenase}}{\rightleftarrows }{\text{Lactate + NAD}}^{\text{+}}\end{array}$

Thus, the above reaction release energy and have a negative value for both energies of the reaction.

Interpretation Introduction

To write: We need to demonstrate the reaction of glycolysis which consumes ATP.

Introduction: Glycolysis is a series of chemical reaction in the body which synthesizes energy in the form of ATP by breaking down glucose molecules. Glycolysis is an extramitochondrial chemical reaction and takes place in the cytoplasm to produce energy in the form of ATP.

Reactions that consume energy to complete would have a positive value $\Delta G$ and also a positive standard state free energy of the reaction $\Delta G^{°\text{'}}$ . While a reaction that releases energy would have a negative value for both the energies $\Delta G$ and $\Delta G^{°\text{'}}$ .

Explanation of Solution

The following reactions of glycolysis consume ATP reactions:

  $\begin{array}{l}\text{Glucose + ATP}\stackrel{\text{Hexokinase}}{\rightleftarrows }\text{Glucose-6-phosphate + ADP}\\ \text{Fructose-6-phosphate + ATP}\stackrel{\text{Phosphofructo kinase}}{\rightleftarrows }\text{Fructose-1,6-biphosphate + ADP}\end{array}$

Thus, the above reaction consumes ATP in the process of Glycolysis.

Interpretation Introduction

To write: the reaction of glycolysis which yields ATP.

Introduction: Glycolysis is a series of chemical reaction in the body which synthesizes energy in the form of ATP by breaking down glucose molecules. Glycolysis is an extramitochondrial chemical reaction and takes place in the cytoplasm to produce energy in the form of ATP.

Reactions that consume energy to complete would have a positive value $\Delta G$ and also a positive standard state free energy of the reaction $\Delta G^{°\text{'}}$ . While a reaction that releases energy would have a negative value for both the energies $\Delta G$ and $\Delta G^{°\text{'}}$ .

Explanation of Solution

The following reactions of glycolysis that yield ATP:

  $\begin{array}{l}\text{1,3-Biphosphoglycerate+ADP}\stackrel{\text{Phosphoglycerate kinase}}{\rightleftarrows }\text{3-P-Glycerate + ATP}\\ \text{Phosphoenol pyruvate +ADP}\stackrel{\text{Pyruvate kinase}}{\rightleftarrows }\text{Pyruvate + ATP}\end{array}$

Thus, the above reaction yields ATP in the process of glycolysis. For each molecule of glucose, the above reaction will take place twice.

Interpretation Introduction

To write: The reaction of glycolysis which is strongly influenced by the changes in concentration of the substrate and product because of their molecularity.

Introduction: Glycolysis is a series of chemical reaction in the body which synthesizes energy in the form of ATP by breaking down glucose molecules. Glycolysis is an extramitochondrial chemical reaction and takes place in the cytoplasm to produce energy in the form of ATP.

Reactions that consume energy to complete would have a positive value $\Delta G$ and also a positive standard state free energy of the reaction $\Delta G^{°\text{'}}$ . While a reaction that releases energy would have a negative value for both the energies $\Delta G$ and $\Delta G^{°\text{'}}$ .

Explanation of Solution

This question can be answered in two ways: The closer the Gibb’s free energy is to Zero, the reaction is closer to the equilibrium state. This indicates that the products and reactants will affect the direction of the reaction. The following reactions of glycolysis are influenced by the changes in concentration of the substrate and product:

  $\text{Glucose-6-phosphate}\stackrel{\text{Phosphoglucoisomerase}}{\rightleftarrows }\text{Fructose-6-phosphate}$

  $\begin{array}{l}\text{Fructose-1,6-biphosphate}\stackrel{\text{Fructosebiphosphate aldose}}{\rightleftarrows }\text{Dihydroxyacetone-P + Glyceraldehyde-3-P}\\ \text{Dihydroxyacetone-P}\stackrel{\text{Triosephosphate isomerase}}{\rightleftarrows }\text{Glyceraldehyde-3-P}\\ {\text{Glyceraldehyde-3-P+NAD}}^{\text{+}}{\text{+ P}}_{\text{i}}\stackrel{\text{Glyceraldehyde-3-P dehydrogenase}}{\rightleftarrows }{\text{1,3-Biphosphoglycerate + NADH + H}}^{\text{+}}\end{array}$

  $\text{1,3-Biphosphoglycerate + ADP}\stackrel{\text{Phosphoglycerate kinase}}{\rightleftarrows }\text{3-P-Glycerate + ATP}$

  $\text{3-Phosphoglycerate}\stackrel{\text{Phosphoglycerate mutase}}{\rightleftarrows }\text{2-Phosphoglycerate}$

  $\text{2-Phosphoglycerate}\stackrel{\text{Enolase}}{\rightleftarrows }{\text{Phosphoenol pyruvate + H}}_{\text{2}}\text{O}$

The second step is the change in Gibb’s free energy with the change in the concentrations. Gibb’s free energy changes with the formula $\Delta G^{°}=-RT\ln K$ , here K is the equilibrium constant.

The equilibrium constant can be easily changed when there is a change in the concentration of products as compared to reactants. These change reactions occur in two steps:

  $\begin{array}{l}\text{Fructose-1,6-biphosphate}\stackrel{\text{Fructose biphosphate aldose}}{\rightleftarrows }\text{Dihydroxyacetone-P + Glyceraldehyde-3-P}\\ {\text{Glyceraldehyde-3-P + NAD}}^{\text{+}}{\text{+ P}}_{\text{i}}\stackrel{\text{Glyceraldehyde-3-P dehydrogenase}}{\rightleftarrows }{\text{1,3-Biphosphoglycerate + NADH+H}}^{\text{+}}\end{array}$

Thus, the above two steps are strongly influenced by the changes in concentration of the substrate and product because of their molecularity.

Interpretation Introduction

To write: The reaction of glycolysis which is at or near equilibrium in the erythrocytes.

Introduction: Glycolysis is a series of chemical reaction in the body which synthesizes energy in the form of ATP by breaking down glucose molecules. Glycolysis is an extramitochondrial chemical reaction and takes place in the cytoplasm to produce energy in the form of ATP.

Reactions that consume energy to complete would have a positive value $\Delta G$ and also a positive standard state free energy of the reaction $\Delta G^{°\text{'}}$ . While a reaction that releases energy would have a negative value for both the energies $\Delta G$ and $\Delta G^{°\text{'}}$ .

Explanation of Solution

The following reactions of glycolysis are the reaction of glycolysis which is at or near equilibrium in the erythrocytes:

  $\begin{array}{l}\text{Glucose-6-phosphate}\stackrel{\text{Phosphoglucoisomerase}}{\rightleftarrows }\text{Fructose-6-phosphate}\\ \text{Fructose-1,6-biphosphate}\stackrel{\text{Fructose biphosphate aldose}}{\rightleftarrows }\text{Dihydroxyacetone-P + Glyceraldehyde-3-P}\end{array}$

  $\begin{array}{l}\text{Dihydroxyacetone-P}\stackrel{\text{Triosephosphate isomerase}}{\rightleftarrows }\text{Glyceraldehyde-3-P}\\ {\text{Glyceraldehyde-3-P + NAD}}^{\text{+}}{\text{+ P}}_{\text{i}}\stackrel{\text{Glyceraldehyde-3-P dehydrogenase}}{\rightleftarrows }{\text{1,3-Biphosphoglycerate + NADH+H}}^{\text{+}}\end{array}$

  $\text{1,3-Biphosphoglycerate + ADP}\stackrel{\text{Phosphoglycerate kinase}}{\rightleftarrows }\text{3-P-Glycerate + ATP}$

  $\begin{array}{l}\text{3-Phosphoglycerate}\stackrel{\text{Phosphoglycerate mutase}}{\rightleftarrows }\text{2-Phosphoglycerate}\\ \text{2-Phosphoglycerate}\stackrel{\text{Enolase}}{\rightleftarrows }{\text{Phosphoenolpyruvate + H}}_{\text{2}}\text{O}\end{array}$

The closer the Gibb’s free energy to Zero, the reaction is closer to the equilibrium state. The following reactions indicate that under cellular conditions the free energy is very small and doesn’t require regulation.

Thus, the above reactions are at or near equilibrium in the erythrocytes.