How is oxygen and carbon dioxide transported in human beings?

Explanation

Haemoglobin transports oxygen molecules to all the body cells for cellular respiration. The haemoglobin pigment present in the blood gets attached to `O_2`
molecules that are obtained from breathing. It thus forms oxy-haemoglobin and the blood becomes oxygenated. This oxygenated blood is then pumped to all the body cells by the heart. After giving away `O_2` to the body cells, blood absorbs `CO_2` which is the end product of cellular respiration. Since, haemoglobin pigment has less affinity for `CO_2, CO_2` is mainly transported in the dissolved form. This de-oxygenated blood gives `CO_2` to lung alveoli and takes `O_2` in return.