CP 3 investigating membrane properties unit 3

state 2 factors that affect the permeability of cell membranes

temperature

concentration of solvents (ethanol)

how is beetroot used to measure the permeability of cell membranes

the higher the permeability the more red pigment that leaks out into the surrounding solution within a given time a colorimeter can be used to determine the absorbance hence concentration of pigment

outline the procedure to investigate the effect of temperature on permeability of cell membrane

• cut beetroot into 8 identical cubes with a scalpel

• place each cube in a different test tube with equal volumes of distilled water

• place each test tube into water baths ranging from 30-80 C leave for 20 minutes

• filter each solution out into a cuvette and measure the absorbance

what are the safety hazards involved in testing the effect of ethanol concentration on membrane permeability

ethanol is an irritant and is flammable keep away from naked flames wear eye protection

keep sharp scalpel away from fingers

handle hot liquid with care

what is the effect of temperature on membrane permeability

increasing temperature results in increased membrane permeability as high temperatures denature the membrane proteins this creates gaps in the membrane for molecules to pass through

increasing temperature also increases the kinetic energy of phospholipids so they move more and are less compact increasing the permeability

what is the exception to the general trend of increasing temperature and membrane permeability

at temperatures below 0 C ice crystals form and pierce the membrane , forming holes for substance to leak out

what is the effect of ethanol concentration on membrane permeability

increasing ethanol concentration leads to increased membrane permeability as ethanol raptures the membrane to form gaps for molecules to pass through