introduction Flashcards
The importance of exchange surfaces
-supply oxygen and nutrients
-get rid of waste products produced during processes
what do multicellular organisms need
-a specialised surface for exchange of substances
-as they are more than 2 layer of cells
what are the factors effecting need for exchange system
-size
-surface area to volume ratio
-level of activity
why is diffusion sufficient for small organisms
-cytoplasm is very close to environment in which they live
-diffusion will supply enough o2 and nutrients to keep cells alive and active
why is diffusion not sufficient in larger organisms
-there’s a longer diffusion pathway
-diffusion is too slow to enable sufficient supply to innermost cells
what can unicellular organisms do
-get all of the substances they need through passive diffusion across a membrane
what do larger organisms have
a greater demand for energy
-high respiration rate so need more substances to be delivered more quickly
how to do SA to volume ratio
Surface area/ volume
how do some organisms increase SA
-adopting a different shape
-such as a flatworm so that it has larger surface area to volume ratio
how does level of activity affect need for exchange system
-in order to release energy for life processes, nutrients required from oxygen and food
when is the need for energy increased
when a mammal needs to keep itself warm (warm blooded)
what are the features of an efficient exchange surface
-large surface area
-thin barrier
-steep diffusion gradient
how does a large surface area allow for efficient exchange
-provides more space/contact for molecules to pass through
how can a large surface area to allow for efficient exchange be achieved
-with folding of walls and membranes
-such as root hair in plants and villi in small intestine
how does a thin barrier allow for efficient exchange
-reduces distance that substances have to travel
-must be permeable to the substances being exchanged
how does good blood supply/steep diffusion gradient allow for efficient gas exchange
-bring fresh supply of molecules from one side, keeping concentration high
-can be efficient removal of molecules from demand side keeping concentration low
-maintain a steep concentration gradient so diffusion occurs rapdily
what is the relationship between concentration gradient and rate of diffusion
-linear relationship
-straight line through origin
-directly proportional
what is the relationship between rate of diffusion and surface area
-if a surface area of the membrane is increased, more space through which particles can move
-more particles crossing in a given time so rate increases
what is the relationship between diffusion distance and rate of diffusion
-indirectly proportional
-rate of diffusion = 1/membrane thickness
-further they have to diffuse means longer it takes so slower rate
-as one doubles the other halves
