The Student Room Group

enzyme-catalysed reaction and enzyme-controlled reaction

as title, are they the same thing? or as the name suggests, is it where chemical reaction is only controlled by enzyme and the other is only sped up by enzymes?
Hi, young lady/man!

Sorry you have not had any help for nearly 2 whole days!
I have not thought of this before, but my analysis of this point would as follows:-

1. Enzymes per se cannot control the rate of a reaction, they can catalyse a reaction in either direction.
2. If the conc of an enzyme is modulated, then we CAN control rate, if the enzyme conc becomes the limiting factor i.e., if the number of active sites available to bind to molecules of substrate determines how fast reaction can proceed.
3. The rate of an enzyme-catalysed reaction [the relative speeds in the two directions] can be controlled by changing other factors, namely temp, pressure [when the substrate and/or product is a gas - if u think about it, you can work this out e.g., if you are synthesizing ammonia gas [Haber process??], then from this reaction:

N2 + 3H2 ------> 2NH3,
you can predict that because 4 moles [effectively 89.6 L] of substrates are producing 2 moles [44.8 L] of product, so you can imagine that increasing the pressure will sort of cause the reaction mixture to be "squeezed"/compressed like, and hence tend to drive the reaction forward cos that will lead to reduction in volume [2 moles from 4 moles] i.e., towards producing ammonia, yeah?]], pH and substrate conc.

I am not in a position to say any more - just explain your interpretation of the title, i.e., explain your reasons for this inference.

(edited 1 year ago)
thank you so much :smile:

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