The scientific models are the simplified visual representations of the complex processes or systems of the natural world.
The models serve many important purposes in scientific investigations as they are used by the researchers to test the predicted hypothesis proposed and to explain the results to another group of peoples which could be a layman.
The 3 D structures of molecules are represented by the globular models and stick key models which even represents the bonds between atoms.
When the cell increases in size, the volume increases faster than the surface area, because volume is cubed where surface area is squared. When there is more volume and less surface area, diffusion takes longer and is less effective.
