required practical 4- permeability of beetroot membranes Flashcards
explain why cubes of fresh beetroot were washed in running water until the water ran clear before the investigation?
to remove excess pigment which was released when beetroot was cut
how would results be affected if pieces of beetroot stuck together?
solution would be a lighter pink colour after the experiment than expected, because less SA would be exposed to the ethanol solution to act on so membrane would be less permeable so less betalin solution would leak out
what affect does ethanol have on the permeability of cell membranes and why?
phospholipids dissolve in ethanol, separating them out and creating gaps in membrane
this increases permeability so more betalin leaks out
what affect does increasing temperature have on the permeability of the membrane?
-increases KE of molecules so phospholipids move more, creating temporary gaps
-denatures proteins by breaking bonds in tertiary structure, loss of tertiary structure means more gaps in membrane so increases permeability
what affect does changing pH have on the permeability of the membrane?
denatures proteins by breaking bonds in tertiary structure, loss of tertiary structure means more gaps in membrane so increases permeability
what things need to be controlled in this investigation?
-SA:V ratio (make size of cylinders same)
-time in water bath
-vol of total solution in tubes (dilutions would be different so reading on colorimeter would be wrong)
-wavelength of light/ coloured filter in the colorimeter
-pH of water (use buffer)
-water potential of water
give one way a student can ensure all beetroot cylinders were kept at the same temp throughout the experiment?
use a thermometer to measure temp at regular intervals AND add hot/cold water if the temp gets too low/ high
how do we reduce uncertainty of equipment?
use equipment with smaller intervals or scale divisions
explain why it is important to use the same volume of solution in each tube?
so results can be compared (basically)
