Which statement about enzymes is correct?

• A. Enzymes are carbohydrates that store energy
• B. Enzymes are lipids that insulate cells
• C. Enzymes are proteins that speed up chemical reactions
• D. Enzymes are nucleic acids that encode information

Answer: (C)

Enzymes are biological catalysts that speed up chemical reactions by lowering the activation energy required for the reaction to proceed. They are primarily proteins with a specific shape that forms an active site where the substrate binds, making the reaction happen more efficiently. This specificity means each enzyme works on particular substrates, guiding metabolic processes in the body. While there are rare RNA enzymes (ribozymes), the classic and most accurate description is that enzymes are proteins that speed up chemical reactions.

The other statements mischaracterize what enzymes are: carbohydrates store energy, lipids insulate, and nucleic acids encode genetic information. In practice, enzymes enable digestion and metabolism by acting on proteins, carbohydrates, and fats under the right conditions of temperature and pH, and they can often be reused after the reaction.