Transport in single celled organisms

• What is the main reactant needed to acquire ATP in bacteria?

  Glucose
• How do reactants enter bacteria?

  Through diffusion across the cell membrane
• How do terrestrial insects balance gas exchange and water conservation?

  • Gases move through tracheal system
  • Methods:
  • Diffusion gradients
  • Mass transport
  • Tracheole water
• What are the three ways gases move in and out of the tracheal system?

  Diffusion gradients, mass transport, tracheole water
• Why does oxygen only diffuse into insects?

  Due to low concentration of O₂ in tissues
• Why does carbon dioxide only diffuse out of insects?

  Because of high concentration of CO₂ in tissues
• What is the role of lactic acid in gas exchange during activity?

  • Lactic acid lowers water potential in cells
  • Water osmoses into cells from tracheoles
  • Increases oxygen intake by lowering tracheole volume
• What happens to water in tracheoles during activity?

  Water osmoses into cells, lowering volume
• What is the effect of decreased tracheal water volume?

  Creates more space for air intake
• How do insects exchange gases?

  Through passive diffusion and physical activity
• What is the maximum distance for effective diffusion of gases in insects?

  Less than 1 cm
• Why can't insects be larger than a certain size?

  Due to limitations of diffusion over distances
• What adaptations help insects succeed as organisms?

  • Small size for efficient gas exchange
  • Exoskeleton to prevent water loss
  • Internal tracheal system for gas transport
• What is the exchange surface for single-celled organisms?

  The cell membrane
• Why can single-celled organisms use simple diffusion?

  They have a large surface area to volume ratio
• What is the issue with water loss in multicellular organisms?

  It can lead to dehydration and cell damage
• What mechanisms do multicellular organisms use to manage water loss?

  • Specialized exchange surfaces
  • Adaptations to minimize water loss
  • Regulation of gas exchange through valves
• What is the structure of the insect respiratory system?

  • Exoskeleton with waterproof cuticle
  • Internal network of tubes: spiracles, trachea, tracheoles
  • Spiracles control gas exchange and water loss
• What happens when spiracles are open?

  Water loss increases significantly
• Under what circumstances do insects open their spiracles?

  When oxygen levels are low