PathwayStep2772 PathwayStep2777 PathwayStep2775 PathwayStep2776 PathwayStep2773 PathwayStep2774 Uptake of Oxygen and Release of Carbon Dioxide by Erythrocytes Authored: May, B, 2011-04-04 Edited: May, B, 2011-04-04 Erythrocytes circulating through the capillaries of the lung must exchange carbon dioxide (CO2) for oxygen (O2) during their short (0.5-1 sec.) transit time in pulmonary tissue (Reviewed in Jensen 2004, Esbaugh and Tufts 2006, Boron 2010). CO2 bound as carbamate to the N-terminus of hemoglobin and protons (H+) bound to histidine residues in hemoglobin are released as hemoglobin (HbA) binds O2. Bicarbonate (HCO3-) present in plasma is taken up by erythrocytes via the band3 anion exchanger (AE1, SLC4A1) and combined with H+ by carbonic anhydrases I and II (CA1/CA2) to yield water and CO2 (Reviewed by Esbaugh and Tufts 2006). CO2 is passively transported out of the erythrocyte by AQP1 and RhAG. HCO3- in plasma is also directly dehydrated by extracellular carbonic anhydrase IV (CA4) present on endothelial cells lining the capillaries in the lung. GENE ONTOLOGYGO:0015701 Pubmed15491402 Pubmed16679072 Pubmed19879980 Reactome Database ID Release 431247673 Reactome, http://www.reactome.org ReactomeREACT_121380 Reviewed: Jassal, B, 2012-04-27 Exchange of Cytosolic Chloride for Extracellular Bicarbonate by Band 3 Anion Exchanger (AE1, SLC4A1) Haldane Effect Passive Transport of Carbon Dioxide out of the Cell by RhAG Passive Transport of Carbon Dioxide out of the Cell by AQP1 Carbonic Anhydrase I/II Dehydrates Bicarbonate H+ + HCO3- -> H2O + CO2