2.40B: Understand the Role of Diffusion in Gas Exchange

DIFFUSION: Passive net movement of particles down the concentration gradient (from region of high concentration to region of low concentration) until equilibrium

ROLE OF DIFFUSION IN GAS EXCHANGE

Diagram showing the Role of Diffusion during Gas Exchange in Alveoli

EXPLANATION For diffusion in gas exchange to be efficient, high concentration gradient needs to be maintained between Alveoli and blood capillaries As a result of gas exchange, Oxygen diffuses from the Alveoli into the bloodstream where it is transported and consumed by cells via cellular respiration, producing Carbon Dioxide as a waste product that diffuses out into the Alveoli to be exhaled Hence, during inhalation, Oxygen enters the Alveoli which results in a high concentration of Oxygen relative to the bloodstream, causing Oxygen to continuously diffuse out from the Alveoli into blood capillaries down the concentration gradient Correspondingly, there is a high concentration of Carbon Dioxide (produced as a waste product in cellular respiration) in the bloodstream relative to the Alveoli, therefore continuously diffusing out into the Alveoli down the concentration gradient to be exhaled out of the lungs A high concentration gradient is maintained between Alveoli and bloodstream to allow continuous gas exchange (diffusion of Oxygen and Carbon Dioxide) to occur