Specialised Exchange Surfaces

• how does an increased surface area produce an effective system


  provides area for exchange to occur, and overcomes limitations of SA:V of larger organisms
• examples of increased surface area


  root hair cells, villi in small intestines
• thin layers


  short diffusion distances so processes are more efficient
• examples of thin layers in systems


  alveoli in lungs and villi
• good blood supply


  steeper the conc gradient = faster rate of diffusion and ensures substances are constantly delivered, maintains steep conc gradient
• examples of good blood supply

  alveoli, gills in fish, villi
• ventilation to maintain diffusion gradient


  maintains conc gradients for gases, increases efficiency
• examples of ventilation


  alveoli and gills
• What do all living things need to survive?

  Oxygen, glucose, proteins, fats, water, and minerals
• Why do living organisms need to absorb certain substances from the environment?

  To keep them alive and support metabolic processes
• What waste products do living organisms need to remove?

  Carbon dioxide, oxygen, ammonia, and urea
• How do single-celled organisms carry out exchange?

  Across their plasma membranes
• How do multicellular organisms perform exchange?

  Smaller organisms across outer surfaces, larger organisms need special exchange surfaces
• Why do larger organisms require special exchange surfaces?

  To facilitate efficient exchange due to their size
• What is the surface area to volume ratio of a cube with sides of 2 cm?

  1. 1
• What is the surface area to volume ratio of a cube with sides of 4 cm?

  1. 5:1
• What is the surface area to volume ratio of a cube with sides of 20 cm?

  1. 3.334
• What happens to the surface area to volume ratio as the size of the cube increases?

  The ratio decreases
• What is a disadvantage of a low surface area to volume ratio?

  It is bad for the exchange of substances
• Why do cells with a low surface area to volume ratio need more supplies?

  Because outer surfaces are not large enough for quick gas and nutrient exchange
• What are the features of a good exchange surface?

  Large surface area, thin barrier, fresh supply of molecules, and removal of molecules
• What are some examples of specialized exchange surfaces?

  Root hairs of plants, respiratory systems of air-breathing animals, hyphae of fungi, small intestine, and liver
• What are the key features of a good exchange surface?

  • Large surface area (folding of membranes and walls)
  • Thin barrier to reduce diffusion distance
  • Fresh supply of molecules on one side to maintain high concentration
  • Removal of molecules on the other side to maintain low concentration
• How does the surface area to volume ratio affect the efficiency of exchange in organisms?

  • Low SA:V ratio is good for conserving heat but bad for substance exchange
  • High SA:V ratio enhances the rate of exchange of gases and nutrients