Why Cells Are So Small

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Why Cells Are So Small
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• Cells are small to maximize their surface are per
  unit volume. The greater the amount of surface
  are per unit volume, the better the cells needs
  for food and waste removal can be met and the
  faster the cell can respond it its environment.

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The Importance of Surface Area

• Cells receive food and eliminate waste for their
  entire volume by way of their surface area.
• Cells respond to their surface area by way of
  their surface area. Cell activities are triggered
  by reception of a signal from its external
  environment on the surface of the cell.

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The Disadvantage of Volume

• As a cells volume increases, it needs more food,
  generates more wastes and responds slower to its
  environment. The response time of a cell depends
  on its ability to transmit a signal to its
  interior and initiate a response. The larger the
  interior of the cell, the slower the response
  time.

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The Limiting Factor Surface Area to Volume Ratio

• As a cell grows, volume increase faster than
  surface area. If a cell grows too large, it does
  not have enough surface area to meet its need for
  food and waste removal or to respond quickly to
  its environment.

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Multicellular Organisms

• Most living things are mulitcellular. Being
  divided into cells provides organisms the
  greatest surface area possible and maximizes how
  efficiently we function

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Robert Wadlow
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Growth Chart

• Age Weight Height Weight to Height Ratio
• 5 105 lbs 5 ft. 4 in. 1.64
• 11 210 lbs. 6 ft. 7 in. 2.73
• 17 315 lbs. 8 ft. ½ in. 3.26

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• With increasing height, Robert Wadlow had a
  disproportionate increase in weight.
• Being a multicellular organism, his body was able
  to cope with the increase in weight and he
  experienced practically normal health.

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Concept Application

• Consider the three topics below and explain how
  the problem of overcoming the limiting factor of
  surface area to volume ratio is overcome
• Gas exchange p 376 to 377
• Small intestine p. 410 to 411
• Plant roots p. 316.