Membrane permeability

Question 1

State two factors affect the permability of cell membranes

Answer 1

• temperature
• concentration of solvents (ethanol)

Question 2

How is beetroot used to meaure the permeability of cell membrane

Answer 2

• higher the permability more red pigment leaks out into surrounding solution within a given time
• colourimeter can be used to determine the absorbance hence concentration of pigments

Question 3

Outline the procedure to investigate the effect of temperature on the permability of a cell membrane

Answer 3

• 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 raanding 30-80 degrees celcius leave for 20 minutes
• filter each solution out into a cuvette and measure absorbance

Question 4

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

Answer 4

• 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

Question 5

Explain the effect of temperature on the membrane permeability

Answer 5

• increasing temperatrure results in increased membrane permeability
• denature membrane proteins
• created gaps in membrane for molecules to pass through
• increases kinetic energy in phospholipids so they move more and are less compact increasing the permeability

Question 6

What is the exception to the general tend of increasing temperature and membrane prermeability

Answer 6

• at temperature below 0 ice crystals form and pierce the membrane forming holes for subtance to leak out

Question 7

What is the effect of ethanol concentration on membrane permeability

Answer 7

• increasing ethanol concentration leads to increased membrane permability
• ethanol ruptures to membrane form gaps more molecules to pass through