Surface Area to Volume

Why Cell Size Matters

A cell is a metabolic compartment where many chemical reactions occur.

• If a cell’s volume is bigger, then more reactions can happen inside it (Yay big cells!) BUT…
• All materials needed for metabolism enter the cell through the cell membrane; the greater the surface area, the larger the amount of materials can enter.
• Each unit of volume requires a specific amount of surface area to supply sufficient amounts of material for metabolism.
• The smaller the cell the faster materials can reach all areas of the cell

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Why is Surface Area : Volume ratio important?

• As a cell grows, its volume increases at a greater rate than its surface area. Therefore, its SA:V ratio decreases. A lower SA:V ratio means the larger cell is less efficient at diffusion.

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• Cells need to be small, as they rely on diffusion to get substances in and out. When a cell grows, there is less membrane for substances to diffuse through, resulting in the cell not receiving substances it needs (like Oxygen). With less efficient diffusion, cell processes slow down and the cell eventually dies.

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