7.1 Specialised exchange surfaces Flashcards
What is a common waste product in gas exchange?
Carbon dioxide
What substances do organisms need?
Oxygen and glucose
Why can single-celled organisms rely on using diffusion alone?
Their metabolic activity is low
Surface area to volume ratio is large
Can multicellular organisms use diffusion for gas exchange?
No, they have too many cells and the distance between cells is too large
It also has a low SA:V ratio
How do you work out the surface area: volume ratio?
Know that a surface area of a sphere is 4 πr^2
volume of a sphere = 4/3πr^3
How is surface area:volume ratio proportionate to how the big the organism is?
Inproportionate, The bigger the organism, the smaller the surface area : volume ratio becomes, and the distances that substances need to travel to reach the centre of the body takes longer (the body cannot meet its demand in oxygen)
What are the 4 characteristics of specialised exchange surfaces?
Increased surface area, thin layers, good blood supply and ventilation
How is increased surface area make the exchange surfaces efficient?
It overcomes the limitations of the small surface area to volume ratio (examples are root hair cells and villi)
How is thin layers make exchange surfaces efficient?
The distances that substances have to travel are short, making the process efficient (examples villi and alveoli)
How is a good blood supply make exchange surfaces efficient?
The steeper the concentration gradient, the faster diffusion can take place. A good blood supply allow substances to be constantly delivered and removed, maintain the concentration gradients (alveoli, gills and villi)
How does ventilation make exchange surfaces efficient?
Being ventilated also helps maintain concentration gradients. (gills, ventilation means there is a flow of water carrying dissolved gases)
