Biochemistry: Concepts and Connections
Biochemistry: Concepts and Connections
16th Edition
ISBN: 9780133900156
Author: APPLING
Publisher: PEARSON
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Chapter 3, Problem 1P
Interpretation Introduction

(a)

Interpretation:

The value of ΔG for the folding of lysozyme at 250 C should be calculated.

Concept introduction:

The standard Gibbs free energy change is related to standard enthalpy change and standard entropy change as follows:

ΔGo = ΔHo -TΔSo

Here,

ΔGo is standard Gibbs free energy change

ΔHo  is standard enthalpy change

ΔSo  is standard entropy change

If ΔG is negative, the forward reaction is spontaneous.

If ΔG is zero, the system is at equilibrium.

If ΔG is positive, the reaction is spontaneous in the reverse direction.

Expert Solution
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Explanation of Solution

Given Information:

The process of a protein folding from an inactive unfolded structure to the active folded structure can be represented by the following equation.

un folded proteinFolded protein

The values of ΔHand ΔS0 for the folding of the protein lysozyme are as follows:

ΔΗo= -280 kJ/molΔSo= -790 J/mol.K

Explanation:

The ΔG for the folding of lysozyme at 250 C can be calculated using following formulae.

ΔG0=  ΔH0- TΔS0                         ……(1)

From the given,

ΔΗ= -280 kJ/molΔS0= -790 J/mol.K= -0.79 kJ/mol.K

Convert temperature from degree Celsius to Kelvin,

T(K)= 25 oC+273.15 = 298.15 K

Substitute the values in the equation (1)

ΔG0=  280 kJ/mol(298.15 K)(0.79 kJ/mol.K)44.58 kJ/mol

Therefore, ΔG for the folding of lysozyme at 25 oC is - 44.58 kJ/mol.

Interpretation Introduction

(b)

Interpretation:

The temperature at which the unfolding of lysozyme is expected to become favorable should be determined.

Concept introduction:

The standard Gibbs free energy change is related to standard enthalpy change and standard entropy change as follows:

ΔGo = ΔHo -TΔSo

Here,

ΔGo is standard Gibbs free energy change

ΔHo  is standard enthalpy change

ΔSo  is standard entropy change

If ΔG is negative, the forward reaction is spontaneous.

If ΔG is zero, the system is at equilibrium.

If ΔG is positive, the reaction is spontaneous in the reverse direction.

Expert Solution
Check Mark

Explanation of Solution

Explanation:

If ΔGo= +ve then the unfolding of lysozyme is favorable.

Temperature can be calculated at ΔGo= 0

Thus,

ΔH0= TΔS0T = ΔH0ΔS0

Putting the values,

T=2800.79=354.4 K

Therefore,at 354.4 K temperature the unfolding of lysozyme is favorable.

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Biomolecules - Protein - Amino acids; Author: Tutorials Point (India) Ltd.;https://www.youtube.com/watch?v=ySNVPDHJ0ek;License: Standard YouTube License, CC-BY