Answer:
Cellular respiration is a complex biochemical process, whose main objective is to achieve that with the use of nutrient elements and in the presence of oxygen, energy, CO2, H2O and hydrogenation are produced as a final result. For vital reasons, since for the cell it can live and function, it needs energy, it is that the cells need the process of cellular respiration. In unicellular organisms, the process is simpler, since the cell membrane is in contact with the source of oxygen, either a liquid medium or an air medium.
In multicellular organisms, the process becomes more complex and much more dependent on multiple factors, because several mechanisms or events are needed, which guarantee oxygen and nutrients reach the different cells, degree of the degree of specialization that they have developed and from the place where they meet.