6.2 - Specialised Exchange Surfaces Flashcards
Why multicellular organisms need specialised exchange surfaces The key features of specialised exchange surfaces (8 cards)
1
Q
Why can’t substances diffuse directly across the cell membrane in multicellular organisms?
2 reasons
A
- Cells are not in direct contact with the environment
- Diffusion distances between cells and their environment are large.
- Larger organisms have higher metabolic rates, so they need more oxygen and glucose.
2
Q
What have multicellular organisms evolved to solve this problem?
A
Specialised exchange surfaces
3
Q
What are specialised exchange surfaces?
A
Structures for transferring materials between cells and the environment
4
Q
What features do specialised exchange surfaces have?
Name 2
A
- Large surface area
- Thin walls
- An extensive blood supply and/or ventilation
- Being surrounded by selectively permeable plasma membranes
5
Q
Why is a large surface area important?
A
Provides a larger area for exchange
6
Q
Why are thin walls important?
A
Minimises diffusion distance
7
Q
Why is an extensive blood supply/ventilation important?
A
Maintains steep concentration gradients
8
Q
Why are selectively permeable membranes important?
A
Controls what substances are exchanged
