7.1 specialised exchange surfaces

Question 1

The need for specialised exchange surfaces

Answer 1

1. high metabolic activity, O2 demands high, produce a lot of CO2
2. Distance between the cells where the O2 is needed and the supply of O2 is too far for effective diffusion to take place
3. the bigger the organism the smaller the the SA:V ratio, so gases cant be exchanged fast enough or in large enough amounts

Question 2

Single celled organisms

Answer 2

1. Amoeba
2. Diffusion alone
3. Low metabolic activity- O2 demand is low, CO2 production is low
4. Large SA:V ratio

Question 3

surface area and volume

Answer 3

sphere:
SA- 4pir2
Vol 4/3pir3

Question 4

Features of an effective exchange surface

Answer 4

Increased surface area- provides area needed for exchange and overcomes limitations of SA:V ratio

Thin layers- short diffusion distance

Good blood supply- steep concentration gradient, substances constantly delivered and removed

ventilation to maintain diffusion gradient- helps maintain concentration gradients