Answered: Step 6 of 11 Use the relation from Step…

Chemistry

10th Edition

ISBN:9781305957404

Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Chapter1: Chemical Foundations

Section: Chapter Questions

Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...

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Question

In physical chemistry, the standard state for a solution is 1 M. In biological systems, however, we define the standard state as 1 ✕ 10⁻⁷ M because the physiological pH is about 7. Consequently, the change in the standard Gibbs energy according to these two conventions will be different involving uptake or release of H⁺ ions, depending on which convention is used. We will therefore replace Δ_rG^o with Δ_rG^o', where the prime denotes that it is the standard Gibbs energy change for a biological process.

(a) Consider the following reactions where x is a stoichiometric coefficient.

(i)	A + B → C + x H⁺
(ii)	C + x H⁺ → A + B

Derive a relation between Δ_rG^o and Δ_rG^o' for reaction (i), keeping in mind that Δ_rG is the same for a process regardless of which convention is used. Repeat the derivation for the reverse reaction, (ii).

(b) NAD⁺ and NADH are the oxidized and reduced forms of nicotinamide adenine dinucleotide, two key compounds in the metabolic pathways. For the oxidation of NADH,

(iii)

NADH + H⁺ → NAD⁺ + H₂

Δ_rG^o is −21.8 kJ·mol⁻¹ at 298 K. Calculate Δ_rG^o'. Also calculate Δ_rG using both the chemical and biological conventions when [NADH] = 1.6 ✕ 10⁻² M, [H⁺] = 3.6 ✕ 10⁻⁵ M, [NAD⁺] = 4.2 ✕ 10⁻³ M, and P_H2 = 0.014 bar.

Step 6 of 11
Use the relation from Step 1 to define A,G using biochemical standard states.
[A]/1
1 M)[B]/1
1 M
A-G = A,GO' + RT In
1 M([H+]/le-07
1е-07| М
Step 7 of 11
Equate the expressions from Steps 5 and 6 and simplify. (Use the following as necessary: R, T, and x.)
1е —7
A,GO
= A,GO' + xRT ln
-xRT ln
1
le -
Step 8 of 11
(b) NAD+ and NADH are the oxidized and reduced forms of nicotinamide adenine dinucleotide, two key compounds in the metabolic pathways. For the oxidation of NADH,
(iii)
NADH + H+ - NAD+ + H2
A,G° is -21.8 kJ•mol-1 at 298 K.
Choose the general reaction that the oxidation of NADH is more similar to.
O reaction (i): A + B – C + x H+
O P reaction (ii): C + x H+ - A + B
Step 9 of 11
Since the oxidation of NADH is more similar to reaction (ii), use the equation from Step 6 to calculate A,G°'at 298 K.
-13
X kJ•mol-1
%3D

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