What red protein in blood carries oxygen throughout the body?

Hemoglobin is the red protein in blood that carries oxygen throughout the body.

It is an iron-containing protein packed inside red blood cells. In the lungs, oxygen binds to the iron-containing heme groups of hemoglobin. Blood then carries the oxygen through arteries to tissues, where changing chemical conditions encourage hemoglobin to release it for cellular respiration.

A single mammalian hemoglobin molecule can bind up to four oxygen molecules. This makes oxygen transport vastly more efficient than relying on the small amount of oxygen dissolved directly in blood plasma. Hemoglobin also helps carry some carbon dioxide and contributes to the blood’s acid-base buffering system.

Myoglobin is a frequent mix-up: it is an oxygen-binding protein found mainly in muscle cells, where it helps store and manage oxygen locally. Collagen provides structural support, while keratin forms tough structures such as hair and nails. Hemoglobin’s red color comes from its heme groups, whose iron-containing structure absorbs light in a way that makes oxygen-rich blood appear bright red.