Cell Size and Efficiency Science 10

• The cell must be able to carry out all life processes

• Transport of materials into and out of the cell is critical

• Cell membrane is the barrier to free exchange between the outside environment and the cytoplasm

• Ability to transport materials must be kept at a maximum

The Ratio of Surface Area to Volume

• If a cell becomes larger, more molecules need to be transported across the cell surface

• Distance any molecule has to travel from the cell surface will increase

• Greater surface area is needed to match the increased need for molecule transport

• Calculate the surface area to volume ratio for different cell sizes

What do these terms mean?

• Area

• Surface Area

• Volume

• Ratio

Calculating the Surface Area to Volume Ratio

• A cube has 6 square faces, each with an area of s^2

• Surface Area of a cube: A = 6s^2

• Volume of the cube: v = s^3

• Surface Area to Volume ratio of the cube

Practice Problems

• Determine the surface area to volume ratio for cubes with different side lengths

The Size and Shape of Organisms

• Limited opportunities for intake of needed materials and expulsion of wastes if very little surface is available

• Inability to take in enough nutrients or remove poisons quickly can affect cell function

• Bigger is not always better for cells

Maximizing Potential

• Each individual cell needs the greatest possible surface area in relation to volume

• Large organisms are multicellular to maximize potential