Exchange Surfaces Flashcards
What are two examples of diffusion
Oxygen and carbon dioxide are transferred between the cells and the environment during gas exchange
Urea (waste product of the breakdown of proteins) diffuses from cells into the blood plasma for removal from the body by kidneys
What does exchanging substances depend on
The organisms surface area to volume ratio
How do you work out surface area
Length times width
How do you work out volume
Length times width times height
Why are exchanging surfaces needed for multi cellular organisms
They have a smaller surface area to volume ratio. Not enough substances can diffuse from their outside surface to supply their entire volume. They need an exchange surface for efficient diffusion. The exchange surface structure has to allow enough of the necessary substances
What are the 4 adaptations of the exchange surface
Thin membrane, so substances have a short distance to diffuse
Large surface area, so lots of a substance can diffuse at once
In animals, they have lots of blood vessels, to get stuff into and out of the blood quickly
Gas exchange surfaces in animals are often ventilated, so air moves in and out
How are lungs adapted so that substances can diffuse through them effectively
Job: transfer oxygen to the blood and to remove carbon dioxide from it
Contains millions of alveoli where gas exchange takes place
What 4 ways are alveoli specialised to maximise the diffusion of oxygen and carbon dioxide
Large surface area
Moist lining for dissolving gases
Thin walls
Good blood supply
How is the small intestine adapted so that substances can diffuse effectively
Contain millions of villi
They increase the surface area so that digested food is absorbed quickly into the blood
What 2 ways are villi adapted so that food can be absorbed quickly
A single layer of surface cells
Good blood supply to assist quick absorption
How is the structure of leaves adapted so that substances can diffuse effectively
Carbon dioxide diffuses into the air spaces within the leaf, then it diffuses into the cells where photosynthesis takes place.
The leafs structure is adapted so that this can happen easily
How is a leaf adapted
The underneath of the leaf is covered in little holes called stomata, which the carbon dioxide diffuses in through
Oxygen produced in photosynthesis and water also diffuse out from the stomata
How is the size of the stomata controlled
Guard cells close the stomata if the plant is losing too much water
Without this plants would wilt
What other 2 ways is the leaf adapted to diffusion
Flattened shape of the leaf increases the area of this exchange surface.
The air spaces inside the leaf increase the area so there’s more chance for carbon dioxide to get into the cells
How are gills adapted for gas exchange
Water (with oxygen) enters the fish through the mouth and passes out through the gills
Oxygen diffuses from the water into the blood in the gills and carbon dioxide diffuses from the blood into the water
