RP 4 Flashcards
INVESTIGATION INTO THE FFECT OF A NAMED VARIABLE ON THE PERMEABILITY OF CELL-SURFACE MEMBRANES
describe a method to investigate the effect of a name variable on the permeability of cell-sufarce membranes
what are the issues with comparing to a colour standard
matching to colour standard is subjective
colour obtained may not match any of the colour standards
why wash the betroot before placing it in water
to wash off any pigment on surface to show that release is only due to [named variable]
why regularly shake each test tube containing cubes of plant tissue
to maintain conc. gradient for diffusion
to ensure all surfaces of cubes remain in contact with liquid
why control the volume of water
too much water would dilute the pigment so solution appears light/more light passes through in colorimeter than expected
so results are comparable
how could you ensure beetroot cylinders were kept at the same temperature throughout the experiment
take readings in intervals throughout experiment of temperature in tube using a digital thermometer
what does a high absorbance suggest about the cell-membrane
more permeable/damaged as more pigment leaks out making surrounding solution more concentrated
explain how temperature affects permeability of cell-surface membrane
as temperature increases, permeability increases
- phospholipids gain kinetic energy and fluidity increases
- transport proteins denature at high temperatures as hydrogen bonds break, changing tertiary structure
at very low temperatures, permeability increases
- ice crystals can form which pierce the cell membrane and increase permeability
explain how pH affects permeability of cell-surface membranes
high or low pH increases permeability
- transport proteins denature as hydrogen/ionic bonds break changing tertiary structure
explain how lipid-soluble solvents (eg. alcohol) affect permeability of cell-surface membranes
as concentration increases, permeability increases
