Where does internal respiration take place?

The process of internal respiration occurs at the cellular level, where oxygen is used by cells to produce energy through metabolic reactions, particularly during the process of cellular respiration. This involves the exchange of gases between the blood and the individual cells in the body.

In this context, once oxygen is transported from the lungs through the bloodstream, it reaches the tissues, where it is taken up by cells and carbon dioxide (a byproduct of metabolism) is released back into the bloodstream. The cells utilize the oxygen to generate adenosine triphosphate (ATP), which is essential for various cellular functions.

While the alveolar level is crucial for external respiration, which involves gas exchange in the lungs and the bloodstream, internal respiration specifically refers to what happens within the cells after oxygen reaches them. Additionally, the lungs and trachea are involved in the transport and exchange of gases but do not participate in the biochemical processes that characterize internal respiration.