Gas Exchange Flashcards
Where does the exchange of materials take place
On the surface of an organism, the materials absorbed and used and assimilated by the cell
What happens to surface area to volume ration, depending on the size of the organism
As the organism gets larger, the surface area to volume ration gets smaller
Gas exchange in single celled organisms
- O2 required to produce ATP during aerobic respiration
- CO2 is a waste product and creates a concentration gradient of these gases in opposite directions
- all organisms rely on diffusion for exchange of O2 and CO2 down their gradients
- these organisms have large enough SA:Vol ratio to meet their gas exchange needs by diffusion across their meme faces
What is fick’s law
Rate of diffusion= surface area x concentration gradient / diffusion distance or pathway
Adaptations to gas exchange in insects - limiting water loss
-Waterproof covering over their body surfaces- a rigid outer Skelton (exoskeleton) covered with a waterproof cuticle
-Small SA:Vol ratio to minimise the area over which water is lost
Movement of oxygen through an insect
- o2 enters the insect through spiracles and into the trachea
- spiracles close
- O2 diffuses through the tracheae into the tracheoles down a conc gradient
- O2 delivered directly to respiring tissues
Describe what a spiracle is
Gas enters and exits the insect through these tiny pores- opened and closed to control water loss by evaporation- open when CO2 levels increasw
Describe what a tracheole is
- Small tubes with thin walls so that the diffusion distance is reduced
- Highly branched so that there is a large surface area
Describe what a trachea is
Network of tubes supported by the strengthened rings- provides tubes full of air so that diffusion is fast
Oxygen diffusion in the tracheal system
- tissues respire using oxygen which reduces the concentration of O2 at the tissue
- O2 moves from an area of higher concentration to lower concentration so moved from the trachea to the tissue
- this lowers the O2 concentration in the tracheae so oxygen moves into the trachea from outside the insect via spiracles
CO2 diffusion in the spiracles
- respiration produces CO2, increasing the concentration at the tissue
- CO2 moves from an area of high concentration at the tissue to the low concentration in the trachea
- CO2 then moved from high concentration in trachea to low concentration out of the insect via spiracles
Ventilation- abdominal pumping
Movement creates a mass movement of air in and out of the trachea- increasing the rate of gaseous exchange- they also have small air sacs in the trachea. Muscles around the trachea contract and pumps the air in the sacs deeper in the tracheoles
Getting additional oxygen during flight
At rest- water can build up in the tracheoles
During flight- insect may partly respire anaerobically and produce some lactate - this lowers the water potential of the muscle cells
As lactate builds up, water passes via osmosis from the tracheoles into the muscle cells
- adaptation draws air into tracheoles closer to the muscle cells and reduces diffusion distance
Explain the structure of the gas exchange in fish
- four gills
- water moves in through mouth and over gills
- gill filaments with many lamaellea at 90o to increase surface area
- water carrying oxygen enters through mouth, passes over lamaellea on the gil filament where most of the oxygen is removed
Give two features of the lamellae
Contain capillaries
Thin epithelium for short diffusion distances
