3.3.1 SA:V ratio

• SA:V- as organisms get bigger, their SA:V ratio decreases, meaning rate also decreases
• Factors that affect the SA:V ratio:

  • Thickness of organism/ cell
  • Shape of organism/ cell
• The surface area to volume ratio (SA:V) determines how fast substances diffuse into or out of cells.
• Each unit of volume (V) of an organism requires a specific amount of surface area (SA) to supply it's metabolism with raw materials. The amount of SA available to each unit of V varies with the size of a cell. As a cell grows, it's SA:V ratio decreases- getting so small it can't supply the raw materials required for it's volume, meaning the cell can't get any larger.