Problem: Oxygen diffuses from the alveolar air across the respiratory membrane (type I cell + shared basement membrane + capillary endothelium) into pulmonary capillary blood. About 98-99% of the O2 binds reversibly to hemoglobin in red blood cells to form oxyhemoglobin; about 1-2% remains dissolved in plasma. This oxygenated blood travels via pulmonary veins to the left heart, then is pumped through systemic arteries to body tissues. In tissues, O2 unloads from hemoglobin and diffuses down its partial-pressure gradient into cells (enhanced by the Bohr effect where higher CO2/H+ promotes O2 release). Please simplify. Need Assignment Help?