Factors affecting cell membrane permeability.

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Factors affecting cell membrane permeability

Aim: to investigate the factors affecting cell membrane permeability of red cabbage, using absolute alcohol (10 cm3), 1 M hydrochloric acid (10 cm3), 1M sodium hydroxide (10 cm3), and distilled water (10 cm3), and change of temperature (40 oC, 65 oC, 100 oC)

Hypotheses: 

If the leaf discs are not rinsed, the distilled water will change colour, because the pigments can escape from the cell destroyed by cutting the cabbage.

If the temperature increases, the solution will become more and more coloured, because the membrane becomes more and more permeable.

Independent variables: for tubes 1-2: rinsing or not rinsing the leaf discs, for tube 3-5: the environment, (for tubes 4-5: pH), for tubes 6-8: temperature

Dependent variable: for tubes 1-2: change of colour of the solution, for tubes 3-5: change of colour of the solution, for tubes 6-8: intensity of colour of the solution

Controlled variables: for all tubes: species, size of leaf discs, amount of solution, for tubes

1-2: pH, for tubes 1-5: temperature, for tubes 6-8: pH

Materials: absolute alcohol, 1 M hydrochloric acid, 1 M sodium hydroxide, distilled water, red cabbage

Equipments: test tubes, test tube rack, beaker, syringe or pipette, thermometer, Bunsen burner, gauze, tripod, implement for cutting the red cabbage into discs, waterproof marker pen, white paper, watch

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Method:

  1. Label test tubes 1-8
  2. Into test tube 1 add 10 cm3 distilled water and three similar sized leaf discs freshly cut from the cabbage, then set the tube aside
  3. Place three rinsed discs into test tubes 2-5
  4. To test tube 2 add 10 cm3 distilled water
  5. To test tube 3 add 10 cm3 alcohol
  6. To test tube 4 add 10 cm3 hydrochloroc acid
  7. To test tube 5 add 10 cm3 sodium hydroxide and set tubes 2-5 aside
  8. Place three more rinsed discs into three test tubes (three each) with ...

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