Exchange surfaces

• What is the main focus of topic 3.1?

  Exchange surfaces
• Why do living cells need a supply of oxygen and nutrients?

  To survive and remove toxic waste products
• How do very small organisms exchange substances?

  By diffusion across the cell surface membrane
• What happens to the need for exchange systems as organisms get larger?

  They require more specialized systems for exchange
• What are the three main factors affecting the need for an exchange system?

  Size, surface area to volume ratio, activity level
• Why is diffusion sufficient for very small organisms?

  All cytoplasm is close to the cell surface
• What are the features of an efficient exchange surface?

  • Large surface area
  • Thin barrier for diffusion
  • Moist environment
  • Good blood supply (in animals)
  • Selectively permeable membrane
• What is the main focus of topic 3.1?

  Exchange surfaces
• Why do living cells need a supply of oxygen and nutrients?

  To survive and remove toxic waste
• How do very small organisms exchange substances?

  By diffusion across the cell surface membrane
• What happens to the need for exchange systems as organisms increase in size?

  They require more specialized systems
• What are the three main factors affecting the need for an exchange system?

  Size, surface area to volume ratio, activity level
• Why do larger organisms need specialized systems for exchange?

  Because diffusion is insufficient for larger sizes
• What is the exchange method for single-celled organisms?

  Diffusion
• What are the features of an efficient exchange surface?

  • Large surface area
  • Thin barrier for diffusion
  • Moist environment
  • Good blood supply (in animals)
  • Selectively permeable membrane
• How does size affect the exchange of substances in organisms?

  • Smaller organisms rely on diffusion
  • Larger organisms need specialized exchange systems
  • Surface area to volume ratio decreases with size
• What is the relationship between activity level and exchange systems?

  • Higher activity levels require more oxygen and nutrients
  • Increased demand for waste removal
  • Specialized systems enhance efficiency in active organisms