Final answer:
Larger cells are less effective because their surface area to volume ratio decreases as they grow, leading to insufficient membrane surface area for necessary diffusion rates.
Step-by-step explanation:
Larger cells function less effectively because as they increase in size, the surface area to volume ratio decreases. This decline is due to the fact that while a cell's surface area scales with the square of its radius, its volume scales with the cube of the radius. Consequently, a cell that grows too large will not have enough plasma membrane surface area to facilitate the required rate of diffusion for the greater volume.
As an example, a cell with a volume of 1 mm³ and a surface area of 6 mm² has a surface area-to-volume ratio of 6 to 1. However, when a cell's volume increases to 8 mm³ and its surface area to 24 mm², the surface area-to-volume ratio drops to 3 to 1. This demonstrates why a larger cell may not effectively support essential processes like nutrient uptake and waste removal, potentially leading to cell division or cell death as a mechanism to restore efficiency.