Final answer:
An enzyme is a protein that acts as a biological catalyst in the body, speeding up chemical reactions such as those in digestion without being consumed.
Step-by-step explanation:
A protein that speeds up chemical reactions in the body is a enzyme. In the context of the digestive system, enzymes play a critical role in chemical digestion by catalyzing the breakdown of large food molecules into smaller molecules that the body can absorb.
An enzyme acts as a biological catalyst, meaning it accelerates biochemical reactions without being consumed in the process. A well-known example of a digestive enzyme would be salivary amylase, which breaks down starch into sugar.
Due to enzymes, reactions that are vital for life, such as those in metabolism, can occur rapidly and efficiently at body temperature. Without the presence of enzymes, these reactions would proceed too slowly to sustain life.