AP BIOLOGY

Detailed explanation-1: -The walls of the alveoli share a membrane with the capillaries. That’s how close they are. This lets oxygen and carbon dioxide diffuse, or move freely, between the respiratory system and the bloodstream. Oxygen molecules attach to red blood cells, which travel back to the heart.

Detailed explanation-2: -CO2 is gaseous molecule and hence it moves in and out of the cell freely by simple diffusion. Diffusion is a process in which the molecules interact and move from a region of higher concentration to a region of lower concentration.

Detailed explanation-3: -CO2 diffuses down its pressure gradient, moving out of the capillaries and entering the alveoli. Oxygen and carbon dioxide move independently of each other; they diffuse down their own pressure gradients.