BIOL1006 Lecture Notes - Lecture 12: Cell Membrane, Prokaryote
Document Summary
Small size, in general, is necessary for all cells, whether prokaryotic or eukaryotic. First, we"ll consider the area and volume of a typical cell. Not all cells are spherical in shape, but most tend to approximate a sphere. You may remember from your high school geometry course that the formula for the surface area of a sphere is 4 r2, while the formula for its volume is 4/3 r3. Thus, as the radius of a cell increases, its surface area increases as the square of its radius, but its volume increases as the cube of its radius. As a cell increases in size, its surface area-to-volume ratio decreases. This same principle would apply if the cell had the shape of a cube. If the cell grows too large, the plasma membrane will not have sufficient surface area to support the rate of diffusion required for the increased volume. In other words, as a cell grows, it becomes less efficient.
