Cell Membranes and Temperature

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Aim

The Aim of this practical was to observe what effect temperature had on the permeability of the cell membrane.

Introduction

Located within the vacuole of beetroot cells is a red pigment call Betalains. Typically these pigments are contained within the cell vacuole by the tonoplast (vacuole membrane), however When beetroot is heated these red pigments escape the vacuole. This experiment aims to explore the effect of temperature on the permeability of the cell membranes (i.e. Tonoplast). ‘The cell surface membrane is the plasma membrane that surrounds cells and forms the boundary between the cell cytoplasm and the environment…..It controls the movement of substances in and out of the cell.’ (Glen Toole and Susan Toole, 2008, p.552). The tonoplast is identical to the cell surface membrane except it surrounds only the vacuole, compared to the cell surface membrane which surrounds the entire cell. A plasma membrane is made up of a phospholipid bilayer. Each layer which consists of a hydrophobic fatty acid tail and a hydrophilic phosphate head. Each layer

Apparatus

• Beetroot
• Size 4 Cork Borer
• White Tile
• Scalpel/Knife
• Ruler
• Water Baths (0°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C) • Plastic Beaker (~250cm3)
• 2 Boiling Tube Racks
• 8 Boiling Tubes
• Crushed Ice
• 8 Thermometers (one per water bath)
• Stopwatch
• Distilled Water
• Pipette
• Cuvette
• Colorimeter

Method

(N.B. – All personal protective equipment must be worn and care must be taken when using the cork borer or Scalpel/knife. All laboratory rules must be followed)

Eight cylinders where cut from the Beetroot, using a cork borer, and then cut to 1cm using a knife or scalpel. Eight water baths were set up at temperatures of 0°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C and 70°C. The 50 60 and 70 water baths were maintained electrically whereas the rest were manual. Eight...
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