Part C Firefly luciferase is the enzyme that allows fireflies to illuminate thei

Question

Part C

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+O2ATPoxyluciferin+lightAMP+PPi If the overall G of the coupled reaction is -7.20 kJ/mol , what is the equilibrium constant, K, of the first reactions at 20 C ? The G for the hydrolysis of ATP to AMP is 31.6 kJ/mol. Express your answer numerically.

Explanation / Answer

G for the hydrolysis of ATP to AMP is 31.6 kJ/mol

G = - 2.303 R T Log K1

- 31.6 = - 2.303 * 0.008314 * 293 *LogK1

LogK1 = 5.63

K1 = 4.26 x 10 5

And for over all coupled reaction,

G = - 2.303 * R T Log K

- 7.20 = - 2.03 *0.008314 * 293 *LogK

LogK = 1.28

K = 19.1

And knowing, K = K1 * K2

Then K2 = 19.1 / (4.26*105) = 4.48 x 10-5

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