... factors that I have found affect the permeability of cell membranes, must somehow destroy part of the cell membrane to allow the pigment molecules to get through and make the surrounding water turn red. (Sources of information: www.fed.cuhk.edu.hk/~johnson/tas/investigation/membrane_teacher.htm C.A.D Discussion on beetroot cells website.) The diagram on the next page shows how the membrane is made of a bilayer of phospholipids with the hydrophilic heads pointing outwards and the hydrophobic tails inside. There are also proteins embedded in the membrane. When the membrane is intact like this the pigment molecules cannot pass through. Here is a diagram of a cell membrane: Effect of temperature: When the temperature of beetroot cells is increased, the proteins and phospholipids of the cell membrane, which are sensitive to temperature variations, are damaged. The proteins are denatured and the lipids are liquefied, so holes are created in the cell membrane, allowing the pigment to come ...

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