Why are enzymes considered catalysts?

Enzymes are considered catalysts because they facilitate chemical reactions without being consumed in the process. This means that they can participate in a reaction and then be available to catalyze subsequent reactions without undergoing any permanent change themselves. Enzymes lower the activation energy required for reactions to occur, which allows reactions to proceed more rapidly and efficiently.

The other options refer to common misunderstandings about the role of enzymes in biological reactions. For instance, while enzymes can influence the rate of reactions, they do not necessarily involve temperature changes as their primary function. Similarly, enzymes do not decrease the overall energy levels of the substrates involved in the reaction, nor are they consumed in the reaction. Instead, they remain unchanged and can be reused multiple times, which is a defining characteristic of a catalyst.