Lecture 20 - Gas Exchange Flashcards
Partial pressure
pressure exerted by one gas in a mixture
- > when air comes in contact with water pressures equalize, so partial pressure in water is the same as air
exchange media
exchange (respiratory) media may be air or water
characteristics of water and air
Air
- > low viscosity and density
- > high PO2 so gas exchange does not need to be efficient
Water
- > dense and viscous
- > dissolved O2 relatively low, so gas exchange needs to be efficient
- > warmer and saltier + less O2
Different types of respiratory surfaces
- > gills
- > tracheal systems
- > lungs
- > leaves
characteristics of respiratory surfaces
respiratory surfaces = exchange systems
- > all cells within contact for diffusion (cells/cell walls must be thin)
- > skin may act as gas-exchange surface
- > restrict size (volume increases faster than surface area)
- > most organisms have a respiratory organ with enormous surface area
gas exchange through gills
- > blood and water flow in opposite directions (counter-current exchange)
- > O2 diffuses from high to low PO2
- > CO2 in opposite direction
tracheal system
series of gradually smaller pipes that extend to (almost) every cell
modifications in aquatic insects
- > aquatic insects with open systems might take an air-bubble along for a dive
- > many closed system insects have gills, usually on the abdomen
why do lungs and gills need ventilation
to keep O2 high and CO2 low at as exchange surfaces
when is pressure breathing positive and negative
Positive = push air in
Negative = push air out
Tidal volume
volume of air inhaled and exhaled at each breath
Vital capacity
tidal volume during maximal inhalation and exhalation
residual volume
air that remains after forced exhilation
How do we control breathing
the medula oblongata and pons controls the breathing rhythm by detecting changes in pH and CO2 concentrations
- > corresponds with metabolic demand and blood circulation
how do plants regulate H2O loss and CO2 gain
with the stromata
- > as K+ accumulates in guard cell (stromate), Ψw(water potential) decreases, and water enters as the cell bow and stromate open
- > K+ efflux has the opposite effect, and stromate closes
