Transportation of oxygen : It ctake splace in the following way :

1. In solution form : Oxygen is less dissolved in plasma–about 3% gets transported in solution form.

2. As oxyhaemoglobin : Oxygen combines with haemoglobin to form oxyhaemoglobin. One molecule of haemoglobin combines with four molecules of oxygen to form oxyhaemoglobin. In the alveoli there is high pO2, low pCO2, lesser H⁺ concentration and lower temperature, these factors favour the  formation of oxyhaemoglobin. Whereas in the tissues, where low pO2, high pCO2, high H⁺ concentration and higher temperature exist, . Since the Haemoglobin molecules take oxygen from respiratory organs and give oxygen to the cells of the body.

Diagram of the exchange of gases

About 97% oxygen is carried in combination with haemoglobin.