Editing Carbon dioxide (section)

=== Transport in the blood ===
{{CO2}} is carried in blood in three different ways. Exact percentages vary between arterial and venous blood.
* Majority (about 70% to 80%) is converted to [[bicarbonate]] ions {{chem2|HCO3-}} by the enzyme [[carbonic anhydrase]] in the red blood cells,<ref name="solarnav">{{cite web |title=Carbon dioxide |url=http://www.solarnavigator.net/solar_cola/carbon_dioxide.htm |url-status=dead |archive-url=https://web.archive.org/web/20080914125551/http://www.solarnavigator.net/solar_cola/carbon_dioxide.htm |archive-date=14 September 2008 |access-date=12 October 2007 |publisher=solarnavigator.net}}</ref> by the reaction:
:{{chem2|CO2 + H2O → H2CO3 -> H+ + HCO3-}}
* 5–10% is dissolved in [[blood plasma]]<ref name="solarnav" />
* 5–10% is bound to [[hemoglobin]] as [[carbamino]] compounds<ref name="solarnav" />

[[Hemoglobin]], the main oxygen-carrying molecule in [[red blood cell]]s, carries both oxygen and carbon dioxide. However, the {{CO2}} bound to hemoglobin does not bind to the same site as oxygen. Instead, it combines with the N-terminal groups on the four globin chains. However, because of [[allosteric regulation|allosteric]] effects on the hemoglobin molecule, the binding of {{CO2}} decreases the amount of oxygen that is bound for a given partial pressure of oxygen. This is known as the [[Haldane Effect]], and is important in the transport of carbon dioxide from the tissues to the lungs. Conversely, a rise in the partial pressure of {{CO2}} or a lower pH will cause offloading of oxygen from hemoglobin, which is known as the [[Bohr effect]].