Question

Question 1: The reaction for the cleavage of fructose 1,6-bisphosphate to dihydroxyacetone phosphate and glyceraldehyde 3-phosphate is catalyzed by the enzyme fructose 1,6-bisphosphate aldolase and has a standard free energy change of ΔG°′ = +23.8 kJ/mol.

A. What is the Keq of the reaction at 37 oC? (R = 8.314 J/°mol)?

B. If the intracellular concentration of fructose 1,6-bisphosphate at equilibrium (ΔG = 0) was 10 mM, what would be the predicted concentration of the products?

C. In cells, the reaction catalyzed by fructose 1,6-bisphosphate aldolase readily occurs to produce dihydroxyacetone phosphate and glyceraldehyde 3-phosphate. Why do you think this is the case especially since the aldolase reaction has a large positive ΔG°′ = 23.8 kJ/mol?

Question 2: You have just discovered a new enzyme that catalyzes the degradation of cellulose to glucose. You hope to commercialize this enzyme ultimately to invent a process for biofuel manufacture. In order to determine how efficient the enzyme is and how fast the enzyme catalyzes the reaction, you have to perform some basic enzyme kinetics. Plot the following enzyme data for the enzyme catalyzed reaction and determine the Km and Vmax.

Answer 1

Question 1:

a) ?G° = +23.8kJ/mol; T=37ºC; R= 8.314 J/ºKmol

ºK = ºC +273.15 = 37º 273.15 = 310.15ºK

?G° = -RTLnKeq

LnKeq = ?G° / -RT = 23.8 kJ/mol / -8.314 J/ºKmolx310.15ºK

LnKeq = 23800 J/mol / -2578.59 J/mol

LnKeq = -9.22985

Keq = 1x10^-4

b) (Products concentration)² = Keq x 10mM = 1x10^-4 x 10mM

(Products concentration)² = 1x10^-3mM

Product concentration = 0.0316mM

c) Enzimatic activity acts reducing the activation energy, and this parameter doesn't affect ?G°

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