Aug 28, 2015
66
26
Status
Pre-Medical
Hi all, I was doing the TPR full length and one of the questions stated that enzymes are only able to speed up a reaction by lowering its activation energy if the reaction is exergonic...

I couldn't find this in any of my biochem or test prep books, and google isn't helping..so I'm starting to freak out

anyone know why this is? I know that enzyme's can lower the activation energy both ways, but why can't they speed up an endergonic reaction?

Thanks in advance
 
Jun 10, 2015
11
4
Status
Pre-Medical
If you consider an exergonic reaction, the catalyst lowers the activation energy for both the forward and the reverse reaction by stabilizing the activated/transition-state complex. If you consider the backwards reaction as an endergonic one (where the free energy is higher than the reactants) you'll realize that a catalyst can speed up the rate of an endergonic reaction as well.

Perhaps the enzyme was one that catalyzed an irreversible reaction?
 

StudyLater

2+ Year Member
Jan 4, 2015
1,993
1,252
Status
Pre-Medical
Hi all, I was doing the TPR full length and one of the questions stated that enzymes are only able to speed up a reaction by lowering its activation energy if the reaction is exergonic...

I couldn't find this in any of my biochem or test prep books, and google isn't helping..so I'm starting to freak out

anyone know why this is? I know that enzyme's can lower the activation energy both ways, but why can't they speed up an endergonic reaction?

Thanks in advance
Pointless thing to freak out about. If you're honestly spending more than 5min researching this problem, you are wasting your time.

Endergonic reactions are nonspontaneous, so I'd view it like: How can you make something that "doesn't happen" happen faster?
 
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