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How do enzymes speed up chemical reactions ?

How do enzymes speed up chemical reactions?

Answer: Some amount of energy must be put in to get the reaction initiated. This energy is required to activate the substances to react. Hence, this energy is called activation energy. In the initial step of the reaction, enzymes by functioning as catalysts, serve to reduce the activation energy required for a chemical reaction to take place. Without altering the process, enzymes speed up the overall rate of reaction.

Figure: Enzymes speed up chemical reactions

The enzyme catalytic process has been described in the following stages

  1. Initially, the substrate binds to the active site of the enzyme, fitting into an active site.
  2. The binding of the substrate induces the enzyme to alter enzyme shape and it leads to fitting more tightly around the substrate.
  3. The active site of the enzyme binds to close proximity of the substrate, breaks the chemical bonds of the substrate and the new enzyme-product complex is formed.
  4. After the reaction, the enzyme releases the final products by decreasing the affinity between enzyme and product.
  5. Finally, the enzyme is ready to involve in another enzymatic reaction again, this means enzymes can recycle the process by binding the other substrate molecule.

Mostly molecular structures of the enzymes are far larger than reactants (substrate) they act on. However, the active site in the enzyme structure is a very small portion having between 3 to 12 amino acids. The remaining portion of the enzymes has around 20 to 200 and more amino acids, which make up the enzyme bulky and maintain the functioning portion (shape) of the enzymes correctly. This extra part of the enzyme is also very important if the active site is to function at the maximum rate.

Once the enzyme converts the substrate to product, the product no longer fits into the active site, immediately releases into the surrounding medium. Leaving the active site free, welcomes the other substrate molecule to fit into it and which makes the other enzymatic reaction.

To know more about how do enzymes speed up chemical reactions, read these posts: 1) Characteristics of enzymes and 2) Mechanism of enzyme action.

 

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