Exchanging Substances

• What is the primary function of the lungs?

  Transfer oxygen to blood and remove carbon dioxide
• What are the tiny air sacs in the lungs called?

  Alveoli
• How do alveoli maximize gas exchange?

  They have a large surface area and thin walls
• What is the surface area of alveoli in humans?

  About 75 m²
• Why do alveoli have a moist lining?

  To dissolve gases for easier diffusion
• What is the role of blood supply in alveoli?

  It helps to maintain a concentration gradient
• What are the tiny projections in the small intestine called?

  Villi
• How do villi aid in digestion?

  They increase surface area for absorption
• What type of cells cover the villi?

  A single layer of surface cells
• How does digested food enter the blood?

  By diffusion and active transport
• What is the function of stomata in leaves?

  To allow gas exchange with the environment
• How do guard cells regulate stomata?

  They open or close stomata based on water loss
• What is the effect of a flattened leaf shape?

  It increases the area for gas exchange
• How do air spaces inside the leaf assist gas exchange?

  They increase the area for carbon dioxide diffusion
• What happens to water vapor in leaves?

  It evaporates and diffuses out through stomata
• What is the gas exchange surface in fish?

  Gills
• How does oxygen enter the blood in fish?

  It diffuses from water into the blood in gills
• What are gill filaments?

  Thin plates that increase surface area for gas exchange
• What do lamellae do in fish gills?

  Increase surface area and contain blood capillaries
• How does blood flow in the lamellae affect gas exchange?

  It maintains a concentration gradient for diffusion
• Why is the concentration of oxygen in water important for fish?

  It ensures maximum diffusion into the blood
• What are the adaptations of alveoli for gas exchange?

  • Enormous surface area (about 75 m²)
  • Moist lining for dissolving gases
  • Very thin walls
  • Good blood supply
• What are the adaptations of villi for nutrient absorption?

  • Millions of tiny projections
  • Single layer of surface cells
  • Very good blood supply
• What are the adaptations of leaves for gas exchange?

  • Stomata for gas entry and exit
  • Guard cells to regulate stomata size
  • Flattened shape for increased surface area
  • Air spaces to enhance diffusion
• What are the adaptations of gills for gas exchange?

  • Gill filaments for large surface area
  • Lamellae with blood capillaries
  • Thin surface layer of cells
  • Countercurrent flow of blood and water