Enzyme Confusion: Lowering Activ. Energy & Bond Strain

[ifihadsomebacon]

So, I know that enzymes are not consumed in the reactions they catalyze, and that they catalyze these reactions by lowering the activation energy. So, in an uncatalyzed reaction, more energy is required to "kick off" the reaction, resulting in the same overall change in free energy. I'm just sort of confused as to how this happens, is the enzyme-substrate₁-substrate₂ transition state just a lower energy state than the substrate₁-substrate₂ state?

Also, I read in my Biology textbook that bond strain was one of the ways that enzymes can catalyze a reaction, but enzymes don't contribute any energy. Doesn't the enzyme putting physical strain on a substrate require energy? Where does that come from?

 

[Borek]

Not sure what you mean by substrate₁-substrate₂ state, I feel like you are making that up.

Have you seen diagrams like this one: https://en.wikipedia.org/wiki/Enzyme#/media/File:Enzyme_catalysis_energy_levels_2.svg

 

[ifihadsomebacon]

Not sure what you mean by substrate₁-substrate₂ state, I feel like you are making that up.

Have you seen diagrams like this one: https://en.wikipedia.org/wiki/Enzyme#/media/File:Enzyme_catalysis_energy_levels_2.svg

I guess I was just trying to refer to the transition state with the enzyme vs. the transition state without the enzyme, sorry if I was unclear. But thank you, that diagram actually helped a lot, all of the ones in my biology textbook are a lot more basic.

 

[Ygggdrasil]

So, I know that enzymes are not consumed in the reactions they catalyze, and that they catalyze these reactions by lowering the activation energy. So, in an uncatalyzed reaction, more energy is required to "kick off" the reaction, resulting in the same overall change in free energy. I'm just sort of confused as to how this happens, is the enzyme-substrate₁-substrate₂ transition state just a lower energy state than the substrate₁-substrate₂ state?

There are many ways that an enzyme can lower the activation energy of a chemical reaction. Almost always, this occurs by lowering the energy of the transition state. This could occur by stabilizing the transition state through interactions of the transition state with the enzyme or it could occur by allowing the reaction to occur through a different transition state than the uncatalyzed reaction. The exact details of how the enzyme does this will depend on the enzyme being studied.

Also, I read in my Biology textbook that bond strain was one of the ways that enzymes can catalyze a reaction, but enzymes don't contribute any energy. Doesn't the enzyme putting physical strain on a substrate require energy? Where does that come from?

In general, the interaction between an enzyme and its substrate is a thermodynamically favorable (exergonic) process that results in a release of free energy. Sometimes, this free energy of binding can be used for purposes such as putting strain on a molecule to promote catalysis. Imagine putting two magnets on either side of a wall that is 5 ft apart (an enzyme active site with sites that interact with different parts of the substrate). Now imagine a 4 ft rubber band with magnets attached on either side (the substrate). If the magnets are strong enough, binding of the magnets on the rubber band to the magnets on the wall can stretch the rubber band and put strain on it. Similarly, strong binding interactions of the enzyme with one part of the substrate can allow the enzyme to force another part of the substrate to adopt a strained conformation.