Exchange Surfaces Flashcards
What can cells use to take in substances they need ?
Cells can use diffusion to take in substances they need and get rid of waste products for example,
Oxygen and carbon dioxide are transferred between cells and the environment during gas exchange
In humans, urea (a waste product from the breakdown of proteins) diffuses from cells into the blood plasma for removal from the body by the kidneys
How to calculate surface area to volume ratio
The larger the organism is, the smaller it’s surface area is compared to its volume
SA:V
Surface area to volume ratio
Find the area of the surface
LXW
Find the volume
LXWXH
The volume is usually smaller than the surface area
Why is it that gas and dissolved substances can diffuse directly into the cell ?
Gases and dissolved substances can diffuse directly into the cell because they have a large surface area compared to their volume so enough substances can be exchanged across the membrane to supply the volume of the cell
Do multicellular organisms have a larger or smaller surface area ?
Multicellular organisms have a much smaller surface area compared to their volume this means they need some sort of exchange surface for efficient diffusion
Exchange surfaces are adapted to maximise effectiveness…
They have a thin membrane so substances only have a short distance to diffuse
They have a large surface area so lots of substances can diffuse at once
Exchange surfaces in animals have lots of blood vessels to get in and out of the blood quickly
Gas exchanges in animals e.g, alveoli are often ventilated- air moves in and out
