Final answer:
The majority of oxygen in the blood is transported while bound to haemoglobin, while the majority of carbon dioxide is dissolved in the blood.
Step-by-step explanation:
The majority of oxygen in the blood is transported while it is bound to haemoglobin.
When oxygen enters the lungs, it binds to iron ions in haemoglobin, forming oxyhemoglobin. This bright red molecule then travels to the body tissues where it releases some of the oxygen molecules, becoming darker red deoxyhemoglobin. The binding of oxygen to haemoglobin is reversible, allowing for the release of oxygen when it is needed in the tissues.
On the other hand, most carbon dioxide in the blood is transported by being dissolved in the blood. About 5 to 7 per cent of carbon dioxide is dissolved directly in the plasma, while about 10 per cent can bind to plasma proteins or enter red blood cells and bind to haemoglobin. The remaining majority is transported as a bicarbonate ion.