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Living things have different levels of organization. Hence growing cells tend to divide and remain small in order to maintain a high SA:Vol ratio suitable for survivalĬells and tissues that are specialized for gas or material exchanges will increase their surface area to optimize material transfer.If metabolic rate exceeds the rate of exchange of vital materials and wastes (low SA:Vol ratio), the cell will eventually die.When this happens, the cell must divide into smaller cells with favorable surface area/volume ratios, or cease to function.Īs a cell grows, volume increases faster than surface area, leading to a decreased SA:Vol ratio

​If the cell grows beyond a certain limit, not enough material will be able to cross the membrane fast enough to accommodate the increased cellular volume. Unfortunately, the volume increases more rapidly than does the surface area, and so the relative amount of surface area available to pass materials to a unit volume of the cell steadily decreases. the surface area to the volume ratio gets smaller as the cell gets larger. The greater the SA/volume ratio is, the faster the cell can remove waste and heat, and absorb oxygen and nutrients essential for the cell to function properly.Īs a cell grows bigger, its internal volume enlarges and the cell membrane expands. The rate of material exchange is a function of its surface area (large membrane surface equates to more material movement). The rate of metabolism of a cell is a function of its mass / volume (larger cells need more energy to sustain essential functions) For most cells, this passage of all materials in and out of the cell.Ĭells need to produce chemical energy (via metabolism) to survive and this requires the exchange of materials with the environment Gases and food molecules dissolved in water must be absorbed and waste products must be eliminated.