Metalloprotein example among the following is?

• A. Hemoglobin
• B. Albumin
• C. Keratin
• D. Collagen

Answer: (A)

Metalloproteins contain a metal ion as part of a prosthetic group that’s essential for the protein’s function. Hemoglobin fits this because its oxygen-carrying capability depends on iron bound in the heme group; the iron ion coordinates with oxygen and changes its state to bind or release O2 as needed. The other proteins shown don’t rely on a metal center for their main role: albumin is a transport protein without a metal-based active site, and keratin and collagen are structural proteins whose properties come from their amino acid makeup and cross-links rather than metal cofactors.