Lesson 7 Surface Area to Volume

  Surface Area and Volume

Surface area and volume may be math terms, but they are used in science too.

When we talk about membrane size, we are actually talking about the surface area of the cell. Surface area is the outside part of an object. In the case of the cell, that outside part is the cell membrane, so the area of the membrane is the same as the surface area of the cell.

Remember, area is the measurement of the space inside a boundary. This is a 2-D measurement; for example, you can find the area of the surface of a desk but you cannot find the entire space of the desk. Area and surface area are always measured in units squared. In the case of the surface area of a cell, we will use millimetres squared (${\mathrm{mm}}^2$) or micrometres squared (${\mathrm{\mu m}}^2$).

To calculate surface area, you will want to find the area of each side and add all those areas together. If the shape is a cube, you can multiply your area of one side by six since all the sides will have the same area and there are six sides on a cube. There are examples of this on the following pages.

Volume, on the other hand, is the space found inside of the cell. It is a 3-D measurement. This is what you would use to find the entire space of the desk or the size of the inside of a cell. It is always measured in units cubed. For cells, we will use millimetres cubed (${\mathrm{mm}}^3$) or micrometres cubed (${\mathrm{\mu m}}^3$).

To calculate volume, you need to multiply the length, width, and height of the object together. There are examples of this on the following pages.