Hemoglobin is composed of?

Hemoglobin is composed of?

• A. A single polypeptide chain binding four iron atoms.
• B. A red-pigmented protein composed of 4 globin chains, each attached to a heme group.
• C. A lipid molecule with iron-binding sites.
• D. A carbohydrate-based protein complex.

Answer: (B)

Hemoglobin is a tetrameric protein made up of four globin polypeptide chains, and each chain binds to a heme group that contains iron. This arrangement gives the molecule its red color and enables reversible oxygen binding: every heme iron can bind one O2 molecule, so the four hemes together allow hemoglobin to carry up to four oxygen molecules per molecule of protein. In adults, the typical pairing is two alpha and two beta globin chains, with one heme group per chain. So the description of a red-pigmented protein consisting of four globin chains, each linked to a heme group, captures both the protein nature and the prosthetic heme components that enable oxygen transport. The other descriptions don’t fit because they imply a single polypeptide, a lipid molecule, or a carbohydrate-based complex, none of which describe hemoglobin’s structure or prosthetic heme groups.

Hemoglobin is a tetrameric protein made up of four globin polypeptide chains, and each chain binds to a heme group that contains iron. This arrangement gives the molecule its red color and enables reversible oxygen binding: every heme iron can bind one O2 molecule, so the four hemes together allow hemoglobin to carry up to four oxygen molecules per molecule of protein. In adults, the typical pairing is two alpha and two beta globin chains, with one heme group per chain. So the description of a red-pigmented protein consisting of four globin chains, each linked to a heme group, captures both the protein nature and the prosthetic heme components that enable oxygen transport. The other descriptions don’t fit because they imply a single polypeptide, a lipid molecule, or a carbohydrate-based complex, none of which describe hemoglobin’s structure or prosthetic heme groups.