Final answer:
An efficiently respiring cell would have a high surface area to volume ratio to allow for effective diffusion of oxygen into the cell and carbon dioxide out of the cell. Larger organisms require complex respiratory systems to maintain this efficiency.
Step-by-step explanation:
Cellular respiration is a process by which cells use oxygen to break down glucose and release energy in the form of ATP. For efficient cellular respiration, oxygen must diffuse into cells and carbon dioxide must diffuse out. This exchange of gases is facilitated by the respiratory system, which includes not only the lungs but also tissues and capillaries where gases are exchanged.
The efficiency of a respiring cell, particularly for larger organisms, depends on having a high surface area to volume ratio. In single-celled organisms, diffusion across the cell membrane is typically enough for supplying oxygen. But as organisms grow larger, they needed to develop more complex respiratory systems like lungs or gills to effectively distribute oxygen. In terms of a cube representing an efficiently respiring cell, it would be one that allows for the highest amount of exchange across its surface, implying significant surface area relative to its volume.
Thus, a cell that manages its oxygen and carbon dioxide levels through diffusion most efficiently would be one that retains a high surface area to volume ratio, ensuring that oxygen can reach all parts of the cell promptly and carbon dioxide can be removed with the same efficiency. The high surface area allows for more oxygen to diffuse in per unit of time, meeting the demand for metabolic processes within the cell. It is essentially for this reason that simple diffusion suffices for small or flat organisms, whereas larger organisms require specialized structures for gas exchange.