Required Practical 4 - investigating affect temperature has on permeability and comparing colour standards

preparing solutions

cut beetroot into equal cubes

rinse to remove excess pigment

add same number of cubes to each test tube containing an identical volume of distilled water

place each test tube in a water bath at a different temperature and leave for the same amount of time

remove beetroot and measure intensity of colour of each solution

methods for measuring intensity of colour of each solution

colour standards

produce a dilution series using known concentrations of beetroot solution and distilled water

compare with colour standards

colorimeter

measure absorbance of known concentrations using a colorimeter

draw a calibration curve with (y) as absorbance against concentration (x)

draw a line of best fit

absorbance value read off to find associated concentration

issues with comparing colour standards

it is subjective

colour obtained may not match colour standard

why the beetroot cubes are washed before starting

to remove excess beetroot and show temperature is the only factor affecting permeability

why shake beetroot solution

ensures all surfaces of beetroot remain in contact with the liquid

ensuring a concentration gradient is maintained

why volume of water is controlled

so the pigment does not become too diluted

how it ensures beetroot solution stays at the same temp throughout the experiment

it is monitored in intervals using a digital thermometer

temp can be increased or decreased if needed

how pH affects permeability of membrane

denatures transport proteins

increases permeability

how temp affects permeability

very low ice crystals form and pierce membrane

high increases fluidity of phospholipids and denatures transport proteins changing their tertiary structure