What is a substance that acts as a catalyst in biochemical reactions?

• A. Protein
• B. Carbohydrate
• C. Lipid
• D. Enzyme

Answer: (D)

A substance that acts as a catalyst in biochemical reactions is known as an enzyme. Enzymes are typically proteins that speed up chemical reactions in the body by lowering the activation energy required for those reactions to proceed. They are essential for various biological processes, including digestion, metabolism, and DNA replication.

Enzymes function by binding to substrates, the specific reactants in a biochemical reaction, and transforming them into products. The unique shape of an enzyme allows it to interact with its specific substrate, ensuring that reactions occur efficiently and effectively. This capability to increase reaction rates without being consumed in the process is the hallmark of catalysts.

While other substances like proteins do serve important roles in the body, not all proteins function as catalysts. Carbohydrates and lipids, while vital for energy storage and structural roles in cells, do not possess catalytic activity in biochemical reactions. Thus, enzymes are the specific class of molecules recognized for their catalytic properties in biological systems.