Why catalysts affect forward and reverse reactions?

In summary, the conversation discussed the concept of enzymes and their specific shape in relation to the reverse reaction. It was mentioned that enzymes can catalyze both the forward and reverse reactions due to the thermodynamics of the process. Additionally, the conversation touched on the comparison between organic and artificial catalysts and how the efficiency of a catalyst can be measured. The conversation ended with a clarification on the "shape" of the active site and its role in enzyme reactions.
  • #1
Pharrahnox
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Based on the very basic understanding on enzymes I have gained from Year 12 Biology and Chemistry, I don't undesrtand why the enzymes specific shape also helps the reverse reaction. I guess my trouble would be due to the simplified diagrams I've seen from Biology, where only the forward reaction is shown to be catalysed.

So if anyone has any explanations or links, that would be great.

Also, a side question, does anyone have a link that compares organic and artificial catalysts; I've heard that enzymes are ridiculously more effective than standard artificial catalysts, but I can't really find what I'm looking for on the interenet. What do you compare? Is it the Turn Over Number?

Anyway, any clarification would be greatly appreciated.
 
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  • #2
Pharrahnox said:
Based on the very basic understanding on enzymes I have gained from Year 12 Biology and Chemistry, I don't undesrtand why the enzymes specific shape also helps the reverse reaction. I guess my trouble would be due to the simplified diagrams I've seen from Biology, where only the forward reaction is shown to be catalysed.

So if anyone has any explanations or links, that would be great.

Also, a side question, does anyone have a link that compares organic and artificial catalysts; I've heard that enzymes are ridiculously more effective than standard artificial catalysts, but I can't really find what I'm looking for on the interenet. What do you compare? Is it the Turn Over Number?

Anyway, any clarification would be greatly appreciated.
I can't comment on the first part, but one quantity used to measure the 'efficiency' of a catalyst is the number of moles of the product per unit mass (often mmol/g).
 
  • #3
In general you have:

reactant + enzyme <-> intermediate complex <-> product + enzyme

So in principle the reaction can go both ways. Typically one direction is preferred due to the thermodynamics of the process.
 
  • #4
Thanks Vagn and Borek for your prompt replies.

I guess I am just incorrectly visualising the "shape" of the active site, and how it bonds with the substrate, whether that be the reactants or products of a particular reaction. It seems strange that an enzyme could not be manufactured to have a "shape" that only works for the forward reaction. Can you think of what exactly I might be missing?
 
  • #5
Enzyme has to fit both the initial and the final "shape", change is continuous.
 
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Likes Pharrahnox
  • #6
Ok, that makes sense. Thanks for your help.
 

1. How do catalysts affect the rate of a chemical reaction?

Catalysts speed up the rate of a chemical reaction by lowering the activation energy required for the reaction to occur. This allows more reactant molecules to reach the energy threshold needed for the reaction to take place, leading to a faster reaction rate.

2. Why do catalysts only affect the rate of a reaction and not the equilibrium?

Catalysts do not affect the equilibrium of a reaction because they do not change the energy difference between the reactants and products. Instead, they lower the activation energy for both the forward and reverse reactions, which allows the reaction to reach equilibrium faster.

3. What is the difference between a homogeneous and heterogeneous catalyst?

A homogeneous catalyst is in the same phase as the reactants, meaning it is either a gas, liquid, or solid in the same state. A heterogeneous catalyst, on the other hand, is in a different phase than the reactants, typically a solid while the reactants are gases or liquids.

4. How do catalysts increase the selectivity of a reaction?

Catalysts can increase the selectivity of a reaction by providing an alternative reaction pathway with a lower activation energy. This allows for the formation of specific products while minimizing unwanted side reactions.

5. Can a catalyst affect both the forward and reverse reactions equally?

Yes, a catalyst can affect both the forward and reverse reactions equally by lowering the activation energy for both reactions. This means that the equilibrium will be reached faster, resulting in a higher yield of products. However, the extent to which a catalyst affects the forward and reverse reactions may differ depending on the specific reaction and catalyst involved.

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