rate of reactions

Question

Hi,

I need some help with this question:

What control experiment should be done to ensure that the rate observed is due to specific enzyme catalysis and not to spontaneous chemical reaction?

I appreciate your help, thank you.

Answer 1

There are several "control" experiments that can be done to ensure that the reaction being studied is mediated by a specific enzyme and not to a general spontaneous reaction.

1. omit the enzyme
2. boil the reaction as heat generally denatures enzymes
3. put in an inhibitor of the enzyme (if known)

All of the above should reduce the rate of reaction if it is indeed catalyzed by a specific enzyme.

Answer 2

The goal for a Catalyst is to speed up the reaction. This is done because the catalyst lowers the activation energy or the energy needed to start the reaction to approach equilibrium. The question seems to draw you more about the kinetics rather than the thermodynamics.

1. One control would be to test for the speed of the reaction. 
2. The control would have no catalyst. 
3. The free gibbs energy or ΔG is not altered whatsoever, so if you are only analyzing this, you would not tell if a catalyst was being used 
4. But on the other hand if you were to measure the activation energy (E_a)) of the catalyzed reaction vs the (E_a) of the un-catalyzed reaction you should see differences in activation energy

Hope this Helps!