Q. 27 Phosphoglucose isomerase was incubated with 0.2 M of glucose 6-phosphate. On reaching
equilibrium, 𝟓𝟓% of glucose 6 -phosphate was converted to fructose 6 -phosphate. The equilibrium
constant for this reaction is ____ .
Correct Answer: The equilibrium constant for the reaction is Keq = 1.22.
Question Restatement
Phosphoglucose isomerase catalyzes the reversible conversion:
Glucose 6-phosphate (G6P) ⇌ Fructose 6-phosphate (F6P)
The enzyme is incubated with 0.2 M glucose 6-phosphate, and at equilibrium,
55% of G6P is converted to F6P.
Calculate the equilibrium constant Keq for this reaction.
Step-by-Step Calculation
Initial concentration of G6P: 0.2 M
At equilibrium, 55% of G6P is converted to F6P:
Amount converted to F6P = 0.55 × 0.2 = 0.11 M
G6P remaining at equilibrium:
0.2 − 0.11 = 0.09 M
Equilibrium Concentrations
- [F6P]eq = 0.11 M
- [G6P]eq = 0.09 M
Equilibrium Constant Expression
For the reaction:
G6P ⇌ F6P
The equilibrium constant is given by:
Keq =
[F6P]eq / [G6P]eq
Substituting the values:
Keq = 0.11 / 0.09 ≈ 1.22
Therefore, the correct answer is Keq ≈ 1.22.
Concept Explanation (For SEO and Exams)
What Is Phosphoglucose Isomerase?
Phosphoglucose isomerase (also known as phosphohexose isomerase or glucose-6-phosphate isomerase)
catalyzes the reversible interconversion of glucose 6-phosphate and fructose 6-phosphate
during glycolysis.
This reaction operates close to equilibrium inside the cell, meaning the direction of the reaction
depends mainly on substrate and product concentrations rather than strong enzymatic regulation.
What Does the Equilibrium Constant Tell You?
An equilibrium constant Keq > 1 indicates that the reaction, as written,
slightly favors product formation at equilibrium.
Here, Keq ≈ 1.22 shows a mild preference for fructose 6-phosphate
when the reaction is written as G6P → F6P.
How This Type of Problem Appears in Exams
In CSIR NET, GATE, and university biochemistry examinations, such questions are designed to:
- Test understanding of percentage conversion and equilibrium composition
- Check the ability to calculate equilibrium concentrations from initial values
- Connect glycolysis reactions with physical chemistry concepts like Keq and ΔG°
Quick Exam Tip:
For any problem giving initial concentration and percentage conversion at equilibrium:
- Calculate equilibrium concentrations
- Substitute into Keq = /[reactants]
$39.00
A Million To One
$36.00
Book Cover Design
$69.00
Create An EBook Cover
$29.00
EBook Cover Design
$24.00
My Book Cover
$30.00
SEO Tricks & Tips
$15.00
The Book Of Art
Original price was: $39.00.$29.00Current price is: $29.00.
The Hypocrite World
$49.00
The Mind Of Leader
$49.00
Web Design Course
Using this approach, the equilibrium constant for this reaction is easily obtained as 1.22.
