exchanging surfaces

• What is the main focus of the next couple of pages in the study material?

  How exchange surfaces in multicellular organisms are adapted for efficient substance movement
• What are the adaptations of exchange surfaces to maximize effectiveness?

  • Thin layers for short distance travel
  • Large surface area for increased substance movement
  • Numerous blood vessels for quick transport
  • Ventilation for air and blood movement
  • Moist surfaces for gas exchange
• What is the primary function of the lungs?

  To transfer oxygen to the blood and remove carbon dioxide
• What are alveoli and their role in gas exchange?

  Alveoli are air sacs in the lungs where gas exchange occurs
• What are the special features of alveoli that maximize diffusion?

  • Enormous surface area (about 75 m² in humans)
  • Very thin walls
  • Moist lining for gas dissolution
  • Good blood supply
• What type of blood returns to the lungs and what does it contain?

  Blood returning from the body contains lots of CO2 and very little oxygen
• How does carbon dioxide move during gas exchange in the lungs?

  CO2 diffuses from the blood (higher concentration) into the alveoli (lower concentration)
• How does oxygen move during gas exchange in the lungs?

  Oxygen diffuses from the alveoli (higher concentration) into the blood (lower concentration)
• What is the primary function of the small intestine?

  To absorb dissolved food molecules into the blood
• What are villi and their role in the small intestine?

  Villi are tiny projections that increase surface area for food absorption
• What features do villi have to assist in absorption?

  • A single layer of surface cells
  • A very good blood supply
• How do leaves facilitate gas exchange during photosynthesis and respiration?

  Leaves use diffusion to exchange O2 and CO2 with the atmosphere
• What adaptations do leaves have for efficient gas exchange?

  • Broad structure for large surface area
  • Thin design for short gas travel distance
  • Air spaces for easy gas movement
  • Stomata for gas diffusion and transpiration
• What are root hairs and their function?

  Root hairs are extensions that increase surface area for water and mineral absorption
• How do root hairs assist in the absorption of water and minerals?

  • Higher water concentration in soil draws water in by osmosis
  • Mineral ions move in by active transport
• Why is a large surface area important for molecules crossing a membrane?

  A large surface area allows more molecules to be close to the membrane