Final answer:
The efficiency of cellular exchange is determined by the surface area-to-volume ratio (SA:V). A spherical cell with a 5 µm diameter is more efficient than a cube-shaped cell with a 7µm side length due to a higher SA:V ratio, which facilitates better nutrient and waste exchange.
Step-by-step explanation:
In biology, the efficiency of cellular exchange of nutrients and wastes is greatly influenced by the surface area-to-volume ratio (SA:V). A higher SA:V means more surface area is available for exchange per unit of volume, which is highly beneficial for cells to function efficiently. Therefore, among different cell models, the most efficient cell in terms of nutrient exchange would be the one with the highest SA:V ratio, while the least efficient would have the lowest SA:V ratio.
For example, a spherical cell with a diameter of 5 µm has a SA:V ratio higher than a cube-shaped cell with a side length of 7µm, because the cube-shaped cell's volume increases faster than its surface area as it grows. Hence, the spherical cell is more efficient in exchanging materials with its environment. In contrast, large cells or those with complex shapes may have a lower SA:V ratio, making them less efficient at exchange and often requiring additional structures like organelles to compensate.