4: Effect of temperature on membrane permeability (beetroot)

Question 1

Independent variable

Answer 1

Temperature of water

Question 2

Dependent variable

Answer 2

% transmission of light through resulting solution

Question 3

Variables to control

Answer 3

Volume of water (10cm3)

S.a. of beetroot

Time beetroot spends in water

The colorimeter filter/wavelength

Part of the beetroot sample taken from (should be from core)

Age, variety and storage of the beetroot

Question 4

Beetroot cell vacuoles contain water soluble pigment called

Answer 4

betalain

Question 5

These pigment molecules are too _____ to pass through membranes

Answer 5

LARGE

Question 6

State 2 factors that affect the permeability of cell membranes.

Answer 6

Temperature
Concentration of solvents (ethanol)

Question 7

How is beetroot used to measure the permeability of cell membranes?

Answer 7

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.

Question 8

At low temperatures:
Plasmalamella and tonoplast are intact, so betalain cannot ______ __________

Answer 8

Pass through

Question 9

At high temperatures:
Proteins in membranes begin to lose tertiary structure, as a result

Answer 9

the membrane becomes more fluid and allows beta lain pigments to leak out.

Question 10

State which filter to use inside the colorimeter

Answer 10

Blue or green

Question 11

State 3 difficulties in the method

Answer 11

maintaining temperature

cutting beetroot to precise lengths

Duration of beetroot in water bath

Question 12

Why are test tubes placed in the water bath for 5 minutes BEFORE beetroot cylinders were added?

Answer 12

To equilibrate tubes to similar starting temperatures

Question 13

Why are beetroot cylinders washed with water before placing in test tube?

Answer 13

To remove excess pigments released from cut cells

Question 14

Outline the procedure to investigate the effect of temperature on permeability of cell membrane.

Answer 14

1. Cut beetroot into 6 identical cubes with a 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°
   C. Leave for 20 minutes.
4. Filter each solution out into a cuvette and measure the
   absorbance using a colorimeter.

Question 15

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

Answer 15

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 16

What is the effect of temperature on membrane permeability?

Answer 16

Increasing temperature results in increase membrane permeability.

Question 17

What is the effect of ethanol concentration on membrane permeability?

Answer 17

Increasing ethanol concentration leads to increased membrane permeability.