In a conjugated protein, the non-protein component is called what?

• A. Prosthetic group
• B. Active site
• C. Cofactor
• D. Subunit

Answer: (A)

Conjugated proteins include a protein portion and a non-protein component that is tightly bound. That non-protein piece is called a prosthetic group. It is permanently attached and essential for the protein’s function, which is why this term is used. A cofactor is a broader term for any non-protein helper molecule for an enzyme and can be more loosely associated. The active site is the region of the protein where substrates bind, not the non-protein component, and a subunit refers to one polypeptide chain in a multimeric protein, not the non-protein part. So, the non-protein component in a conjugated protein is the prosthetic group.