Diffusion & the alveoli (Edexcel GCSE Biology Combined Science): Flashcards

Movement of particles from higher to lower concentration

Passive transport (no energy required)

Distance, concentration difference, surface area

Increases rate (particles have more kinetic energy)

One cell thick (short diffusion distance)

Millions of alveoli provide large total surface area

Maintains concentration gradient for diffusion

Helps gases dissolve and diffuse across membrane

Rate $\propto$ (surface area $\times$ conc. diff.) / thickness

Oxygen and carbon dioxide