Biochemistry: Concepts and Connections (2nd Edition)
Biochemistry: Concepts and Connections (2nd Edition)
2nd Edition
ISBN: 9780134641621
Author: Dean R. Appling, Spencer J. Anthony-Cahill, Christopher K. Mathews
Publisher: PEARSON
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Chapter 2, Problem 19P
Interpretation Introduction

(a) Interpretation:

If the enzyme is more active at pH 3.5 or 4.5 should be explained.

Concept Introduction:

The acidic group in amino acid is protonated at lower pH value and basic group is protonated at high pH value. Thus, for a amino acid, if pKa>pH, acidic or −COOH group is protonated and if pKa<pH then basic group is protonated.

Interpretation Introduction

(b) Interpretation:

The fraction of the enzymes active at pH 4.07 should be determined.

Concept Introduction:

The Henderson-Hasselbalch equation that relates pH and pKa of solution is as follows:

    pH=pKa+log[A][HA]

Here, pH is negative log of hydrogen ion, pKa is negative log of acid dissociation constant, [HA] is concentration of weak acid and [A] is concentration of conjugate base.

Interpretation Introduction

(c) Interpretation:

The pH value at which enzyme show 78% of maximal activity.

Concept Introduction:

The pH of solution can be calculated from Henderson-Hasselbalch equation as follows:

    pH=pKa+log[A][HA]

Here, pH is negative log of hydrogen ion, pKa is negative log of acid dissociation constant, [HA] is concentration of weak acid and [A] is concentration of conjugate base.

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