What is an enzyme?

An enzyme is indeed a biological catalyst that lowers the activation energy of a chemical reaction. This is significant because enzymes facilitate biochemical reactions by enabling them to occur at a much faster rate and at lower temperatures than they would without the presence of an enzyme. They do this by providing an alternative reaction pathway that requires less energy to achieve the transition state.

Enzymes are typically proteins, though some RNA molecules can also function as enzymes (ribozymes). By lowering the activation energy, enzymes help maintain the efficiency and regulation of metabolic processes crucial for life.

The other choices do not accurately describe enzymes. Inorganic catalysts do not qualify as enzymes since enzymes are intrinsically linked to biological processes and are organic in nature. Similarly, while non-protein substances may enhance reaction rates, most enzymes are protein-based. Lastly, enzymes are not products of chemical reactions; rather, they are catalysts that facilitate those reactions. Understanding the definition and role of enzymes in biological systems is fundamental to the study of biochemistry and enzyme kinetics.