Question

Question #1da6b

Answer 1

The exchange takes place in the capillaries, it takes place because of diffusion due to entropy.

Explanation:

The arteries coming from the heart supply the capillaries in the lungs with blood that is low in Oxygen and high in Carbon Dioxide.

The Carbon Dioxide (`CO_2`) will flow from the capillaries to the alveoli because the concentration of the carbon dioxide in the alveoli is less than in the pulmonary capillaries. Diffusion always causes movement from the high concentration to the low concentration due to the second law of thermodynamics called entropy. Carbon dioxide is produced in our muscles, in the process cellular respiration.

Oxygen (`O_2`) will flow from the alveoli into the pulmonary capillaries. The alveoli have a high concentration of Oxygen ( approximately 20%). The pulmonary capillaries have a very low concentration of Oxygen.
This difference in concentrations will cause diffusion from the alveoli to the capillaries.

The veins leaving the lungs will be high in Oxygen and low in Carbon Dioxide. This blood high in Oxygen will be pumped by the heart to the systemic tissues. The systemic capillaries will allow the Oxygen to diffuse into the cells where the Oxygen will be used in Cellular Respiration to produce the energy necessary for life.