module 3 - 7.1 specialised exchange surfaces Flashcards
why do we need to exchange material?
for survival e.g. food, oxygen, water
what is the main thing that all organisms need to exchange?
gas (CO2, O2)
why cant we diffuse oxygen and carbon dioxide through the skin?
too thick, diffusion distance too great
what features must an effective gas exchange system have?
concentration gradient
SA:V ratio
moist inner wall of alveoli (turns gas to aqueous solution)
what are some reasons for exchange systems?
- large multicellular organisms have a small SA:V
- cells in center of organism wouldn’t receive any materials if multicellular organs survived on diffusion alone
- multicellular organisms have high metabolic rate
- need to exchange lots of materials fast
what makes the exchange of substances by diffusion easier?
larger the SA:V
why do multicellular organisms require specialist exchange surfaces?
they have a small SA:V
why can single celled organisms survive using diffusion alone?
because its a shorter diffusion pathway between cytoplasm and edge
what does a steep gradient mean for diffusion?
faster diffusion
how does large SA make gas exchange more efficient?
provides larger area for material exchange to occur
how do thin layers make gas exchange more efficient?
creates a short diffusion distance for gases, increases speed of exchange
how does blood supply make gas exchange more efficient?
constant blood supply maintains large diffusion gradient, makes sure exchanged substances are constantly moving to area needed
how does ventilation make gas exchange more effeicient?
maintains diffusion gradient, makes process faster & more efficient
