Which term describes proteins that contain a non-protein prosthetic group?

• A. Conjugated proteins
• B. Simple proteins
• C. Fibrous proteins
• D. Globular proteins

Answer: (A)

Proteins that include a non-protein component, a prosthetic group, are called conjugated proteins. The prosthetic group is an integral part of the molecule and often essential for the protein’s function—examples include heme groups in cytochromes, metal cofactors in various enzymes, or carbohydrate parts in glycoproteins. Because the presence of this non-protein part defines them, conjugated proteins are distinguished from simple proteins, which consist only of amino acid chains without any attached non-protein parts. Shape classifications like fibrous or globular describe overall form rather than whether a prosthetic group is present, so they don’t identify this concept.