Investigating membrane properties

• 2 factors that affect the permeability of cell membranes

  • temperature
  • concentration of ethanol
• Beetroot for permeability of cells

  • higher permeability, more red pigment leaking out
  • colorimeter can be used to determine absorbance, hence concentration of pigment
• Procedure to investigate effect of temperature on permeability of cell membrane

  1. cut beetroot into 8 identical cubes with scalpel
  2. place each cube in a different test tube with equal volumes of distilled water
  3. place each test tube into water baths ranging from 30 - 80 degrees. leave for 20 minutes
  4. filter each solution out into a cuvette and measure the absorbance
• Safety hazards for testing effect of ethanol on membrane activity

  • ethanol is an irritant and is flammable
  • keep away from naked flames
  • wear eye protection
  • keep scalpel away from fingers
  • handle hot liquid with care
• Temperature on membrane permeability

  • increasing temp mean increased permeability
  • high temps denature the membrane proteins, this creates gaps in the membrane for molecules to pass through
  • also increases kinetic energy of phospholipids so they move more and are less compact, increasing permeability
• Membrane permeability below 0 degrees

  • below 0, ice crystals form
  • piercing the membrane, forming holes for substances to leak out
• Ethanol on membrane permeability

  • increasing ethanol concentration leads to increased membrane permeability
  • ethanol ruptures the membrane to form gaps for molecules to pass through