Explanation:

Enzymes are biological catalysts that speed up chemical reactions without being consumed or permanently altered in the process. They work by providing an alternative reaction pathway with a lower activation energy.

* Catalyst: An enzyme acts as a catalyst, facilitating a reaction without being changed itself.

* Activation Energy: Enzymes lower the activation energy required for a reaction to occur, making it proceed faster.

* Specificity: Enzymes are highly specific, meaning they only catalyze certain reactions involving specific substrates.

Key Concepts:

* Active Site: The region on the enzyme where the substrate binds and the reaction takes place.

* Substrate: The molecule that an enzyme acts upon.

* Product: The molecule that is formed as a result of the enzymatic reaction.

Conclusion:

While enzymes may undergo temporary conformational changes during the catalytic process, they return to their original state after the reaction is complete. Therefore, they are not altered by the reactions they catalyze.