Question

What is true about the surface area to volume ratio in living organisms?

It limits the size and shape of living things

It goes up as organisms get bigger

It means that diffusion becomes more efficient in larger organisms

It prevents diffusion from being used to obtain nutrients or eliminate wastes in any type of organism

Answer 1

The correct option is Option 1 – It limits the size and shape of living things.

The cells of living organisms are microscopic and cannot be seen with the naked eye. One of the reasons why cells cannot grow beyond this microscopic scale is because of the surface area-to-volume ratio. The surface area is calculated as the area outside the cell, which is the plasma membrane. The space that is present inside the cell is its volume. The surface area to volume is a ratio that is obtained by dividing the surface area of the cell over its volume. If the ratio is big, the cell is small. Bigger cells have smaller surface area-to-volume ratios.

Surface area-to-volume is directly related to the efficiency of the cell. Each cell has dedicated function in the body. Within the cell, there exists a complex network of structural and functional organelles, with thousands of metabolic reactions taking place. The by-product of these reactions generates waste which needs to diffuse out of the cell. Similarly, the cell also needs to take up essential nutrients and solutes via diffusion through its plasma membrane. The cell also receives various inputs in the form of chemical signals from other cells with respect to function and reproduction. These signals usually reach the interior of the cell by traversing through the plasma membrane. If the surface area to volume is too small, then all the above process will take a longer time in exerting their downstream effects. Hence, the size and shape of a cell is limited by its surface area-to-volume ratio.