Topic 8 - Exchange Of Materials Flashcards
Why do large multicellular organisms require specialist exchange surface?
Small SA/V ratio
Diffusion insufficient to provide all cells with required oxygen and nutrients, and to remove all waste products.
Exchange surfaces increases rate of diffusion and shortened diffusion distance.
Why do some multicellular organisms require specialised exchange surfaces? Eg trees
Trees have a large number of leaves that provide a large SA/V ratio for diffusion.
How does the size of an organism affects its surface area to volume ratio?
The larger the object the smaller the SA/V ratio
Name some of the substances transported into and out of the body?
Oxygen
Carbon dioxide
Water
Dissolved food molecules
Urea
How does oxygen enter and carbon dioxide leave cells?
The diffuse into and out of cells
How does water enter cells?
It diffuses into cells by osmosis
How do food molecules and mineral ions enter cells?
They are dissolves into water which diffuses into cells.
