cell biology : surface area to volume ratio

• What concept explains why multicellular organisms require exchange surfaces and a transport system?

  Surface area to volume ratio
• How do gills increase the rate of gas transport in fish?

  They provide a large surface area for gas exchange
• What is the process by which molecules move in and out of cells?

  Diffusion
• What happens to oxygen and carbon dioxide in the process of diffusion in cells?

  Oxygen diffuses into cells and carbon dioxide diffuses out
• What is the surface area to volume ratio of a cube with a side length of 1 mm?


  1. 1
• How do you calculate the surface area of a cube with a side length of 1 mm?

  Surface area = 6 * (1 mm * 1 mm) = 6 square mm
• What is the volume of a cube with a side length of 1 mm?

  Volume = 1 mm * 1 mm * 1 mm = 1 cubic mm
• What is the surface area to volume ratio of a cube with a side length of 2 mm?

  1. 1
• How do you calculate the surface area of a cube with a side length of 2 mm?

  Surface area = 2 mm * 2 mm * 6 = 24 square mm
• What is the volume of a cube with a side length of 2 mm?

  Volume = 2 mm * 2 mm * 2 mm = 8 cubic mm
• What happens to the surface area to volume ratio as organisms get larger?

  It falls sharply
• Why can't multicellular organisms rely solely on diffusion for gas exchange?

  Cells in the center are too far from the surface
• What are the two ways animals have solved the problem of gas exchange?

  Special structures for gas exchange and a transport system
• How do fish obtain oxygen from water?

  Oxygen-rich water passes into the mouth and flows over gills
• What role do gill filaments play in gas exchange?

  They allow gases to pass in and out of the blood
• What adaptations do gill filaments have to increase the rate of diffusion?

  They provide a large surface area, have a thin membrane, and an efficient blood supply
• Why is a high concentration gradient important for gas exchange in gills?

  It ensures that diffusion is as efficient as possible
• What are the key adaptations of gill filaments for efficient gas exchange?

  • Massive surface area
  • Thin membrane for short diffusion pathway
  • Efficient blood supply to maintain concentration gradient
• How does the surface area to volume ratio affect multicellular organisms?

  • As size increases, the ratio decreases
  • Larger organisms cannot rely on diffusion alone
  • Need for specialized structures and transport systems
• How do multicellular organisms ensure efficient gas exchange?

  • Use specialized structures (e.g., lungs in mammals)
  • Have a transport system to distribute gases