Why is a high surface to volume ratio important to cells?


Why is a high surface to volume ratio important to cells?

In: Biology

The cell must pull nutrients from the outside and push out waste. The rate that this happens is based on the amount of surface area of the cell. Maximizing the surface area is the best way of ensuring that the cell gets enough nutrients and can excrete waste.

Cells exchange nutrients, gases and everything through their membrane, so the rate at which they can get new things and eject excess things is defined by their surface area. But their internal consumption and production is defined by their volume because it’s full of organelles which do stuff. So, if a cell is too big, it wouldn’t be able to supply itself.

Oxygen and other important molecules travel via diffusion. Diffusion is the natural tendency for substances to move from areas of high concentration to low concentration. A cell with a low surface area to volume ratio can’t get oxygen etc. from outside of the cell to all of the areas of the cell that need it fast enough to sustain life. The surface area of a cell needs to be large enough to allow for nutrients to be delivered to all of the areas of a cell. Alternatively, the volume of a cell has to be small enough to allow for efficient movement of molecules.

Diffusion. Diffusion is a natural effect that just happens. When there is an unbalance of something, like molecules things tend to balance themselves. (Entropy, over time gradients dissappear. So if you got two liquids with different concentration of whatever they will mix to create one liquid with no concentration difference.) So as diffusion happens on its own it doesn’t require energy so its the most efficient way to exchange molecules. But it can only happen between the cell’s edge/membrane and the surrounding stuff. And you want to get the molecules to go all over the cell. So you cant have too much volume with little area. As a cell’s size grows its volume grows faster than its surface area. So the larger you are the less effective diffusion becomes, thats why your lung’s surface area is super large, the individual cells use diffusion to exchange air, so you need a lot.