Catalysts/Enzymes regarding Entropy

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Sydney Wu 2M
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Joined: Fri Jul 22, 2016 3:00 am

Catalysts/Enzymes regarding Entropy

Postby Sydney Wu 2M » Thu Mar 02, 2017 3:18 pm

Entropy is a measure of disorder, so if you make delta S less positive, you decrease entropy (more order), and if you make delta S less negative, you increase entropy (more disorder), correct?

In lecture, we were told that catalysts and enzymes speed a reaction by putting reactants in the correct orientation before the reaction occurs. Wouldn't this mean delta S*+ becomes more negative since the catalyst/enzyme is bringing order to the reactants? I understand that when you put a less negative delta S*+ in the delta G*+ formula you increase delta G*+ and have a faster reaction, but conceptually I am confused...

Thank you!

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Re: Catalysts/Enzymes regarding Entropy

Postby Justin_Yi_1J » Thu Mar 02, 2017 4:00 pm

A way to think about it is using the equation ΔG° = ΔH° - TΔS°. Since a catalyst/enzyme will place the substrates into a more ordered state so that the substrates can more readily react, ΔS° will be higher with a catalyst than when there is no catalyst present. When ΔS° is higher, ΔG° lower and therefore the energy barrier is reduced. Both ΔG° and ΔS° will be positive no matter what in a kinetically controlled reaction. However, we can reduce ΔG° by raising the magnitude ΔS° using a catalyst or enzyme.

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