Exchange Surfaces

Question 1

why is diffusion important in cells?

Answer 1

it is needed to take in substances they need to get rid of waste products:
•Oxygen and Carbon dioxide are transferred between cells and the environment during gas exchange
•in humans, urea diffuses from cells into the blood plasma for removal from the body by the kidneys

Question 2

what does the the ability for an organism to exchange substances with its environment depend on?

Answer 2

Surface area to volume ratio (SA:V)

Question 3

what is the equation for surface area?

Answer 3

length x width (pg. 20 cgp book)

Question 4

what is the equation for the volume of a cube?

Answer 4

length x width x height

Question 5

why do multicellular organisms need exchange surfaces?

Answer 5

*in single celled organisms gases and dissolved substances can diffuse directly in and out of the cell as they have a larger surface area compare to it’s volume so enough substance can be exchanged across the membrane to supply the volume of the cell
*multicellular organisms have smaller surface areas compared to their volume so not enough substances can diffuse from their outside surface to supply their entire volume so some sort of exchange surface is needed

Question 6

how are exchange surfaces adapted to maximise effectiveness?

Answer 6

•they have a thin membrane so substances only have a short distance to diffuse
•they have a large surface area so lots of substance can diffuse at once
•exchange surfaces in animal have lots of blood vessels to get stiff into and out of the blood quickly
•gas exchange surfaces in animals are often ventilated too (air moves in and out) e.g. alveoli