Which statement best describes the term 'biocatalyst'?

A biocatalyst is best defined as a catalyst composed of biological molecules, primarily enzymes, that facilitates and accelerates biochemical reactions within living organisms. By helping to speed up cellular processes, biocatalysts are crucial for various metabolic functions, including digestion, DNA replication, and energy production.

This definition aligns perfectly with the correct answer since biocatalysts specifically refer to biological agents that enhance the rate of chemical reactions in biological systems, thus playing a key role in sustaining life. Enzymes, as a type of biocatalyst, lower the activation energy required for reactions to occur, which makes metabolic processes more efficient.

The other choices do not accurately capture the essence of a biocatalyst. For instance, a substance that slows down reactions runs counter to the function of a biocatalyst, as it would inhibit rather than promote chemical activity. While proteins are involved in energy creation, not all proteins function as biocatalysts, and energy production is just one aspect of cellular activities. Hormones, while they regulate various functions in the body, do not have the catalytic role that biocatalysts have in biochemical reactions.