Aim:    To investigate the effects of temperature on the movement of pigment through beetroot cells.

Plan:    We will be using beetroot as the pigment is clearly visible and we will be able to use a colorimeter to measure the amount of pigment that has diffused through the plasma membrane.

To make this a fair practical we will be using beetroot cylinders of the same width and length. Temperature affects the plasma membranes on the outer layers of the beetroot cylinders by giving more energy to the phospholipids making the plasma membranes more fluid. This weakens the semi-permeable membranes and increases diffusion and allows more particles in and out of the cell therefore explains the effect temperature will have on pigment movement through the cell membranes. This results in osmosis of the water into the plant cell and the cells become turgid and plasmolyzed causing the pigment to be released from the cells vacuole.

  1.  Precautions

When carrying out an experiment, safety precautions must be thought about to ensure the safety of the pupil.

  • Hot water can be extremely dangerous and cause serious damage to skin especially as we will be working with temperatures around 85oC.
  • Safety goggles should be used to protect eyes when heating water as near boiling water could scold and blind.
  • Hair should be tied up and lose items of clothing should be tucked away or removed in case they catch fire when heating the water.
  • Only hold the borers when in use because they are sharp and you could easily cut yourself.
  • Walkways should be clear and the work surface should be clear except for equipment.
  • When cutting beetroot you must be careful as the scalpel is extremely sharp and could cause a very deep wound.
  • The Bunsen burner itself can reach high temperatures and an accident could happen so you should always place a heat proof mat underneath your Bunsen burner to protect the surface.
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  1. Hypothesis

My hypothesis is that when the temperature increases, more tonoplasts will rupture and more red pigment will leak out of the cell. The heating of the phospholipids bi-layer will destroy the hydrogen bonds of the vacuole membrane and pigment will be released from the vacuole so therefore the absorbance reading will increase and the transmission will decrease.

 

Apparatus:

For this practical I will use the following equipment.

  • Test-tube rack to hold the test tubes.
  • 8 test tubes for holding beetroot cylinders and water.
  • Sticky labels for marking test tubes.
  • Graduated syringe (10cm3) used ...

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