gas exchnage Flashcards
1
Q
Why can small multicellular organisms rely on diffusion
A
They have large SA:V ratio
- large SA means maximum gas exchange occurs
- smaller volume means smaller distances across the body
2
Q
Why can’t larger mammals rely on diffusion
A
They have smaller SA:V ratio
- for surface area mammals have evolved to maximise gas exchange ( lung )
- volume is still a problem as the distances between the body and exhnage surface are large
3
Q
How is diffusion distances solved for mammals
A
Mass transport system such as the circulatory system
4
Q
How is the lung adapted for gas échange
A
- large SA of alveoli
- numerous capillaries around alveoli
- thin walls of alveoli and capillaries -> shorter diffusion distance
5
Q
What is Ficks Law of diffusion
A
Rate of diffusion = SA x permeability constant x ( difference in conc)
all over the thickness of the membrane
6
Q
Three features of efficient gas exchange
A
- steep conc gradient maintained my blood supply
- large surface area
- thickness of gas échange surface
