oxygencarrying

Oxygencarrying refers to the capacity of a substance or system to transport molecular oxygen from sites of availability to tissues and cells that require it for metabolism. In animals and humans, oxygen transport is a central function of the circulatory and respiratory systems and underpins aerobic energy production.

In vertebrates, most oxygen is carried in blood bound to hemoglobin within red blood cells. Each hemoglobin molecule can bind up to four O2 molecules, enabling efficient transport because oxygen is little soluble in plasma. Oxygen loading occurs in the lungs, where alveolar PO2 is high; unloading happens in tissues with lower PO2, aided by factors such as lower pH, higher temperature, and higher concentrations of 2,3-bisphosphoglycerate (2,3-BPG). Myoglobin in muscles serves as a local oxygen store and facilitates diffusion to mitochondria.

Other oxygen-carrying mechanisms exist across life: some invertebrates use hemocyanin (copper-based) instead of iron-containing hemoglobin; dissolved plasma oxygen, while present, is a minor component under normal conditions. Disorders of oxygencarrying include anemia (low red cell mass or hemoglobin concentration) and methemoglobinemia (hemoglobin with reduced oxygen affinity). Hypoxemia and hypoxia describe insufficient arterial oxygen or tissue oxygenation, respectively.

In medicine and research, supplemental oxygen therapy and devices deliver higher arterial oxygen levels when needed. Artificial oxygen carriers, such as perfluorocarbon emulsions or hemoglobin-based substitutes, have been explored as blood substitutes, but clinical use remains limited due to safety and regulatory challenges.