Gas exchange

• Gas exchange process

  Process where oxygen is taken up from the environment and carbon dioxide is released as a byproduct of cellular respiration the bi-directional change happens via diffusion
• 3 Factors that affect the efficiency of gas exchange

  1. concentration gradient
  2. surface area ( for exchange) to volume ratio
  3. Distance over which exchange occurs
• Main site of gas exchange?

  Alveoli- in the lungs. lungs contain tiny sacs called alveoli where gas exchange takes place.
• How to work out surface area to volume ratio

  Surface area (cm^2) / volume (cm^3)
• Surface area and volume of a sphere

  SA: 4πr²

  Vol: 4/3 πr³
• higher SA: volume ratio

  1. A higher SA:V ratio (small cells/ organisms)- small volume allows faster diffusion of substances like oxygen and nutrients to all organelles (shorter diffusion pathway) and diffusion alone can supply their cells oxygen to carry out aerobic respiration and generate ATP. Large SA:V allows for max absorption of nutrients and gases and removal of waste products.
• 1. A lower SA:V ratio

  2. A lower SA:V ratio (larger organisms/ more than 2 layers of cells)- less SA for absorption of nutrients and gases and removal of waste products in relation to the volume . Greater volume means longer diffusion distance to the cells and tissues. This all means diffusion is less efficient, so adaptations (e.g. range of Tissue) are needed to increase the surface area to volume ratio at their exchange surface.
• Percentage change

  (New-old)/old x 100
• Why is Maintenance of a deep concentration gradient by diffusion critical

  Critical so oxygen to diffuse from a higher concentration to lower and capillaries. If this didn’t happen once equilibrium is oxygen would stop diffusing.
• How are Alveoli adapted for gas exchange

  • Covered in capillaries which provideslarge SA so more diffusion of oxygen to blood and more co2 out of blood
  • 1 cm thick alveoli wall and capillary wall so short diffusion distance
  • Good blood supply from capillaries create steep concentration gradient for co2 and o2
• Ficks Law


  Ficks law