PART A Consider these hypothetical chemical reactions: 1. A <--> B, Delta G = 13

Question

PART A

Consider these hypothetical chemical reactions:

1. A <--> B, Delta G = 13.2 kJ/mol

2. B <--> C, Delta G = -28.5 kJ/mol

3. C <--> D, Delta G = 7.70 kJ/mol

What is the free energy, Delta G, for the overall reaction, A <--> D?

Express your answer with the appropriate units.

Delta G = ?

PART B

Firefly luciferase is the enzyme that allows fireflies to illuminate their abdomens. Because this light generation is an ATP-requiring reaction, firefly luciferase can be used to test for the presence of ATP. In this way, luciferase can test for the presence of life. The coupled reactions are

Luciferin + O2 <--> Oxyluciferin + light

ATP <--> AMP + PP1

If the overall Delta G of the coupled reaction is -8.10kJ/mol, what is the equiilibrium constant, K, of the first reactions at 16 degrees C? The Delta G for the hydrolysis of ATP to AMP is -31.6 kJ/mol.

Explanation / Answer

A D , dG = dG1 + dG2 + dG3 = 13.2 -28.5 +7.7 = -7.6 KJ/mol Part B) dG of 1st rxn = dG of total rxn - dG of 2nd rxn = -8.1 -(-31.6) = 23.5 KJ/mol dG = -RT lnK 23.5 x1000 = -8.314 x (273+16) ln K K = 5.65 x10^ -5

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