What are enzymes?

Enzymes are biological catalysts that play a crucial role in speeding up chemical reactions within the body without being consumed in the process. This means that enzymes can facilitate various biochemical reactions by lowering the activation energy required, allowing these reactions to occur more efficiently and rapidly.

By being utilized multiple times, enzymes contribute to the metabolic processes essential for life, such as digestion and energy production. For example, in the digestive system, enzymes help break down complex molecules like proteins, lipids, and carbohydrates into simpler forms that can be absorbed and utilized by cells.

The other options describe functions that do not accurately represent what enzymes are. For instance, substances that slow down chemical reactions would contradict the primary role of enzymes. Chemicals that break down nutrients into smaller molecules refer more to the specific actions of certain enzymes but do not encompass their broader catalytic function. Structures that protect cells from toxins are related to other biological mechanisms and do not define enzymes at all. Thus, recognizing enzymes as biological catalysts is essential in understanding their significant role in biochemical processes.