Exchanging substances Flashcards
what is the surface area to volume ratio used for (SA:V)
working out how easy it is for an organism to exchange substances with its environment
what is the equation for surface area
length x width
what is the equation for volume
length x width x height
why can gases and dissolved substances diffuse directly into single-celled organisms
they have a large surface area compared to their volume so enough substance can be exchanged across the membrane to supply the volume of the cell
why do multicellular organisms need some sort of exchange surface for efficient diffusion
they have a smaller surface area compared to their volume which means that not enough substances can diffuse from their outside surface to supply their entire volume
how does gas exchange happen in the lungs
they contain millions of air sacs called alveoli (where gas exchange happens)
what do the alveoli have to maximise diffusion of oxygen and CO2
an enormous surface area
a moist lining for dissolving gases
very thin walls
a good blood supply
