branch CELLS

==Diffusion and Cell Size== The larger a cell is, the greater the surface area available for diffusion. So why are cells so tiny? Although increasing the size of a cell would increase its surface area, it would also increase the cells volume and thus its demand for nutrients etc. In fact, increasing the size of the cell has a much greater effect on the cells volume than it does on its surface area. If a cell is too large, nutrients simply aren’t able to diffuse through the entire volume of the cell quickly enough. [image:] Materials must be able to reach all parts of a cell quickly, and when volume is too large relative to surface area, diffusion cannot occur at sufficiently high rates to ensure this. Smaller cells have a much greater surface area to volume ratio allowing material to diffuse throughout the entire volume of the cell quickly and efficiently. ==Surface Area : Volume== Surface area to volume ratio can also be used to explain the shape of many cells / cellular surfaces. For example the folds inside the mitochondria or the flat pan-cake like structures inside chloroplasts provide a greater surface area on which specific reactions can occur. The folds in the lining of our stomachs or the tiny cellular, finger-like projections that protrude from the wall of the intestine (villi) all act to increase the surface area without increasing the overall size or volume of the organ.