Amount of $CO_{2}$ in expired air is about (in $\%$)

Explain the exchange of gases in short.

Compared to $O_2$,the diffusion rate of $CO_2$ through the diffusion membrane per unit difference in partial pressure is much higher. Explain.

Diffusion of gases occurs in the alveolar region only and not in the other parts of the respiratory system. Why?

Which of the following factors affect the rate of diffusion?

Through which process is oxygen transported from the lungs to the tissues?