How do body cells exchange oxygen and carbon dioxide?

It's red blood cells that do this. They containa chemical called heamoglobin a protein that makes them red at the same time as bonding with gas particles. As they pass through the lungs cells pick up oxygen then flow through the blood and into tissues where they drop the oxygen and bond with carbon doixide and any other waste gases. They then flow back aroubd through the heart that pumps them into the lungs again and where they then drop the waste gases.