AQA GCSE Combined Science Trilogy · 8464
Specification 4.1.3.1 · Paper 1
Revise: Diffusion and factors affecting its rateDiffusion also allows gas exchange in the lungs. Oxygen diffuses from the air in the alveoli—the small air sacs in the lungs—into the blood. Carbon dioxide diffuses in the opposite direction, from the blood into the alveoli, and is then breathed out.