Activation Energy, Transition State & Reaction Intermediates Explained

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    Activation Energy
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Discussion Overview

The discussion centers around the concepts of activation energy, transition states, and reaction intermediates in the context of chemical reactions, particularly focusing on multistep reactions and enzyme interactions. Participants explore the relationships between these concepts and their representations in reaction diagrams.

Discussion Character

  • Homework-related
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant expresses confusion about whether the top of a reaction diagram represents the transition state or reaction intermediates, noting that the transition state is not a stable chemical species.
  • Another participant clarifies that in a multistep reaction, reaction intermediates are located in the valleys between the peaks that represent transition states.
  • A different participant questions whether the activation energy is lowered by the binding energy released when the enzyme binds to the transition state, suggesting a sequence of energy reductions through noncovalent interactions.
  • Another participant challenges this view, stating that the enzyme does not bind to the transition state, but rather that the transition state forms after the enzyme binds to the substrate.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between enzymes and transition states, with no consensus reached on whether enzymes bind to transition states or if the transition state forms after enzyme-substrate binding.

Contextual Notes

Participants highlight the complexity of the concepts involved, including the definitions and roles of activation energy, transition states, and reaction intermediates, which may depend on specific reaction mechanisms.

lha08
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Homework Statement


I'm a little confused as to the concept of activation energy, transition state, and reaction intermediates...For example, I know that the activation energy is the difference between the ground state of the reactants and the transition state but on a diagram, does the top hill represent the transition state or the reaction intermediates? The thing is that supposedly the transition state is not a chemical species, its just a fleeting moment, but is this particular state represented by the reaction intermediates or is this state just between the formation of the ES and EP complexes?


Homework Equations





The Attempt at a Solution

 
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If there is a multistep reaction, intermediates are in the valleys between tops occupied by transition states.
 
Borek said:
If there is a multistep reaction, intermediates are in the valleys between tops occupied by transition states.

I'm just wondering, in terms of the activation energy, if the enzyme binds complementary to the transition state, is the activation energy first lowered by the binding energy that is released when some weak noncovalent interactions are formed between the enzyme-substrate complex, and then the binding energy that is released when the ES noncovalently binds further lowers the activation energy?
 
I can be wrong, but as far as I can tell enzyme doesn't bind to the transition state, transition state appears after enzyme binds to the molecule.
 

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