Final answer:
Cell size is primarily limited by the cell's ability to take in nutrients and remove wastes through the plasma membrane, as the surface area-to-volume ratio decreases with increasing cell size.
Step-by-step explanation:
Cell size is limited by the cell's ability to remove wastes and take in nutrients. This is because as a cell grows, its surface area-to-volume ratio decreases, making it difficult for the plasma membrane to have enough surface area to support the diffusion required for the larger volume. In both prokaryotic and eukaryotic cells, the plasma membrane functions as the "skin" of the cell, determining the rate at which materials can enter and exit. In eukaryotic cells, which are larger than prokaryotic cells, this limitation is even more pronounced due to their increased complexity and the presence of membrane-bound organelles.
Diffusion through the plasma membrane is essential for supplying nutrients and oxygen and for expelling waste products. As cell size increases, acquiring sufficient materials to support internal processes becomes more challenging due to the relative decrease in surface area compared to volume.