6.1 - Specialised Exchange Surfaces

Question 1

Key features of specialised exchange surfaces (4):

Answer 1

1. A large SA - provides a larger SA which substances can be exchanged
2. thin walls - minimise the diffusion distance
3. Extensive blood supply/ventilation - maintains steep conc. gradients
4. surrounded by selectively permeable plasma membranes - controls what substances are exchanged

Question 2

Why do multicellular organisms require specialised surfaces? (3)

Answer 2

1. cells aren’t in direct contact with the external environment
2. diffusion distances between cells and their environments are large
3. Large organisms have higher metabolic rates - need more O2 and glucose