Exchanging materials Flashcards
exchange of oxygen
- alveoli in lungs
- needed for respiration
exchange of CO2
- alveoli in lungs
- waste product of metabolism
exchange of water
- nephrons in kidney
- needed for cells to function properly
exchange of dissolved food molecules
- small intestine
- needed for respiration
exchange of mineral ions
- small intestine
- needed for cells to function properly
exchange of urea
- nephrons in kidney
- waste product of metabolism
What happens as organisms get bigger?
surface area to volume ratio decreases
they can’t rely on diffusion
need specialised exchange surfaces and transport systems
adaptations of capillaries
- wall is one cell thick so diffusion happens quickly
- large surface area:volume so more diffusion can take place
- continual flow of blood maintains a concentration gradient
- substances continue to diffuse out the capillary
- substances are carried to other areas of the body
Why do substances need to diffuse out of capillaries quickly?
the blood is continuously moving quickly
What would happen if the blood in capillaries stopped flowing?
- concentration of substances would balance
- removing the concentration gradient
-preventing diffusion from occurring
diffusion
movement of molecules from an area of higher concentration to an area of lower concentration
surface area:volume
given as 1 value:
SA / V
e.g. 0.6, 0.3
Why do cells have to be small?
so there is enough surface area to meet the demands of the cells volume
a bigger cell needs more materials, but hasn’t got a large enough SA for all of them to diffuse in
material can only get so far through a cell membrane, so in a cell that is too big the material won’t reach the middle
