6.2 - Gas exchange in single-celled organisms and insects

• How does gas exchange occur in single-celled organisms ?

  Via diffusion across the cell-surface membrane
• Why does the increased SA in insects conflict with conserving water ?

  There's a larger area for water to evaporate from
• What 3 main components make up the tracheal system of an insect ?

  Spiracles, trachea, tracheoles
• What prevents the trachea from collapsing ?

  Strengthened rings of cartilage
• How is the diffusion distance between tracheoles and respiring cells short ?

  Have an extensive network throughout all the body tissues
• What are the 3 ways that gas exchange occurs in the tracheal system ?

  Along a diffusion gradient, Mass transport, Via the ends of tracheoles that're filled of water
• How does mass transport in the tracheal system of insects work ?

  Contraction of muscles can squeeze the trachea, enabling mass movements of air in and out
• How does the ends of tracheoles being filled with water enable gas exchange in insects ?

  When active, muscle cells will anaerobically respire and produce lactate, this is soluble and lowers the water potential of the cells causing water to move into the cells from the tracheoles via osmosis, volume in tracheoles decreases and draws in air, so final diffusion pathway is in a gas rather than liquid so is faster
• Why do insects keep their spiracles closed most of the time ?

  To prevent water loss