Which process refers to the gas exchange in the cells?

Cellular respiration is the correct answer because it specifically refers to the biochemical process in which cells convert glucose and oxygen into energy (ATP) while producing carbon dioxide and water as byproducts. This process takes place at the cellular level, allowing cells to extract energy from nutrients for various functions.

Pulmonary ventilation, on the other hand, refers to the mechanical process of moving air in and out of the lungs. It does not involve the exchange of gases at the cellular level.

External respiration describes the exchange of gases (oxygen and carbon dioxide) that occurs between the air in the alveoli of the lungs and the blood in the pulmonary capillaries. This is a crucial process for oxygenating blood but takes place before the gases reach the cells.

Internal respiration pertains to the exchange of gases between the blood and the tissues. Although it is related to gas exchange, it is not the process of energy production that occurs within the cells; rather, it refers to how oxygen is delivered to tissues and how carbon dioxide is taken back into the bloodstream.

Understanding these distinctions clarifies why cellular respiration is the correct choice for identifying the process of gas exchange specifically at the cellular level.