Gaseous Exchange

Why is gaseous exchange necessary

  • Supplies body with oxygen

  • Removal of CO2 - failure to remove can cause formation of carbonic acid, which can lower pH


Requirements to maximise Gaseous Exchange

  1. Large surface area

  2. Transport system (blood in blood vessels) - blood must be close to gaseous exchange surface

  3. Thin and permeable - for quick and easy diffusion

  4. Extras

    Must be well protected to prevent dessication and injury

    Must be well ventilated


HOWEVER :

Surface area is the amount of oxygen that can be absorbed, while Volume is the amount of oxygen the organism requires

The LARGER the organism, the SMALLER the surface area to volume ratio

Unicellular organisms rely on diffusion and have a large surface area to volume ratio

Processes

EXTERNAL GASEOUS EXCHANGE

  • High concentration of OXYGEN (O2) in ALVEOLUS, which dissolves in the moisture of the alveoulus and diffuses through alveoulus wall and capillary wall into the blood

  • High concentration of CARBON DIOXIDE (CO2) in CAPILLARY, which dissolves through capillary and alveolus wall into the alveolus


INTERNAL GASEOUS EXCHANGE

  • Cellular respiration takes place in tissue of organism : requires O2 and produces CO2

  • O2 levels decrease and CO2 levels increase

  • Oxygen moves from capillaries to tissue cells

  • Carbon Dioxide moves from tissue cells to capillaries