Surface Area to Volume Ratios Chapter 10: Cell Division

Surface Area A measure of the number of square units needed to cover the faces or surfaces of a figure. Surface Area = Length x Width x # of sides

Example of Surface Area A cube has 6 equal sides, so the Surface Area = 6 x L2  Example: The length of one side of a cube is 0.5 cm. Calculate the Surface Area of the cube. Surface Area = 6 x L 2 = 6 x (0.5)2 = 6 x 0.25 = 1.5 cm2

Volume The amount of space occupied by a three-dimensional object Volume = Length x Width x Height

Example of Volume A cube has 6 equal sides, so the Volume = L3 Example: The length of one side of a cube is 0.5 cm. Calculate the volume of the cube. Volume = L3= (0.5)3 = 0.125 cm3

Example of Surface Area to Volume Ratio 0.5 x 0.5 x 6 = 1.5 cm 2 Volume 0.5 x 0.5 x 0.5 = 0.125 cm 3 Ratio of Surface Area to Volume 1.5/0.125 = 12:1

Surface Area to Volume Ratios Changes in the surface area to volume ratio are important in determining an organism’s size, and help explain some of the modifications seen in larger-bodied organisms. Imagine a cell shaped like a cube. As the length of the sides of a cube increases, its volume increases faster than its surface area, decreasing the ratio of surface area to volume. If a cell gets too large, its surface area is not large enough to get enough oxygen and nutrients in and waste out efficiently.