In biochemistry, which term describes a protein that acts as a biological catalyst by increasing the rate of a chemical reaction without being consumed?

• A. Cofactor
• B. Substrate
• C. Enzyme
• D. Inhibitor

Answer: (C)

Verified step by step guidance

1. Understand the role of each term in the context of biochemical reactions: a cofactor is a non-protein molecule that assists enzymes, a substrate is the molecule upon which an enzyme acts, and an inhibitor is a molecule that decreases enzyme activity.
2. Recall the definition of a biological catalyst: it is a substance that increases the rate of a chemical reaction without being consumed or permanently altered in the process.
3. Identify which term fits this definition: the protein that acts as a biological catalyst by increasing reaction rates without being consumed is called an enzyme.
4. Recognize that enzymes lower the activation energy of reactions, thereby speeding up the reaction without changing the equilibrium or being used up.
5. Conclude that among the given options, 'enzyme' is the correct term describing a protein that functions as a biological catalyst.