Hemoglobin is a protein found in red blood cells that is essential for transporting oxygen from the lungs to the tissues throughout the body. It contains iron, which binds oxygen molecules, allowing hemoglobin to carry oxygen efficiently. Each hemoglobin molecule can bind up to four oxygen molecules. This oxygen delivery is critical for aerobic respiration, which powers cellular metabolism
. Hemoglobin also helps transport some carbon dioxide, a waste product of metabolism, from the tissues back to the lungs for exhalation. The iron in hemoglobin gives red blood cells their characteristic red color
. Structurally, hemoglobin is made of four protein subunits (two alpha and two beta chains in adults) each containing a heme group with an iron atom that binds oxygen. Variants of hemoglobin exist, such as fetal hemoglobin (Hb F) and sickle hemoglobin (Hb S), which differ in oxygen affinity and function
. Normal hemoglobin levels vary by age and sex but typically range from about 12 to 18 grams per deciliter of blood. Low hemoglobin levels can indicate anemia, leading to symptoms like fatigue, weakness, and shortness of breath due to insufficient oxygen delivery to tissues
. In summary, hemoglobin is the iron-containing oxygen-transport protein in red blood cells that enables oxygen delivery to tissues and carbon dioxide removal, playing a vital role in maintaining the body's metabolic functions.
