Before the formation of oxyhaemoglobin, the O ₂ has to pass through _________ membranes from the alveolar air.

Step-by-step solution

To form oxyhaemoglobin, oxygen from the alveolar air must diffuse into the red blood cells (RBCs) where haemoglobin is present. During this process, the O ₂ molecule has to pass through the following three cellular membranes: 1. Squamous epithelium of the alveoli (Alveolar membrane) 2. Endothelium of the alveolar capillaries (Capillary membrane) 3. Plasma membrane of the red blood cell (RBC membrane) Note: The basement substance present between the alveolar epithelium and capillary endothelium is a non-cellular mat