Gas Exchange in Single-Celled Organisms and Insects (Gas Exchange in…
Gas Exchange in Single-Celled Organisms and Insects
Gas Exchange in Single-Celled Organisms
Small t/f large SA:V
O2 absorbed by diff. across body surf., covered by cell - surface membrane
CO2 diff. out of body surface
Cell wall of living cell, no barrier to diff.
Respiratory Gases Move in + out of Tracheal Sys.:
Along diff. grad.
When cells respire O2 is used up t/f conc. toward end of tracheoles fall = diff. grad. + causes O2 to diff. from tubes to cells. CO2 produced by cell res. = diff. grad. in opposite direction, from cells to tubes.
Diff. in air, much more rapid than in H2O, t/f respiratory gases r exchanged more rapidly
Contraction of mucles = insects can squeeze trachea enabling mass movements of air in + out
Further speeds up ex. of respiratory gases
Ends of Tracheoles, Filled with H2O
Muscle cells, around tracheoles anaerobically respire, produces lactate, soluble + lowers water potential
H2O moves to cells from tracheoles by OSMOSIS, water @ ends decreases vol. + t/f draws further air in2 them t/f final diff. path. is in gas rather then liquid phase + t/f diff is more rapid
Inc. rate @ which air is moved in the tracheoles but leads to greater H2O evap.
Gas Exchange in Insects
Insects conserve water
Gas ex. SA required conflicts with conserving water b/c H2O will evap.
For gas ex. insects use TRACHEAE
Supported by strengthened rings that prevent collapse
Divide into smaller dead-end tubes, TRACHEOLES
Extend throughout boddy tissue
Atmospheric air with O2 is brought directly to respiring tissues b/c, short diff. path. from tracheal to any body cell
Gas Exchange in Insects 2
Gases enter + leave trough SPIRACLES, on body surface
May be open/closed by a valve
When open, H2O vapour can evap.
Periodically open to allow gas ex.
Most of time spiracles are closed, prevent water loss
Efficient method of transport
Relies on diff. 2 ex. gases b/w environment and cells
For diff to be effective...
Diff. path. needs to be shot = insects are small
Length of diff. path. limits size of insects