Investigating the effect of temperature on permeability of membranes

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Ehtisham kiani                                                                                              01/05/2007        

Investigating the effect of temperature on                            permeability of membranes

The investigation will look into the effect of temperature on membrane permeability using beetroot tissue.

Background

Cells of the beetroot contain a red dye called anthocyanin. Under normal conditions the dye is held within the cell by the cell membrane. However in an experiment to show the effect of various reagents (such as alcohol and detergent) on membrane permeability, the structure of the membrane is altered and the red dye leaks out of the cells. The reagents alter the phospholipid component of the membrane.

Prior knowledge:-

Plant cell walls contain cellulose. Cellulose is a polymer of beta glucose. Cellulose fibres have a high tensile strength; this helps the cell to withstand large pressures that develop within it as a result of osmosis. Without this the wall would burst when in a dilute solution. Cellulose fibres are freely permeable allowing water and solutes to reach the plasma membrane.

Cytoplasm is an aqueous material varying from a fluid to a jelly like consistency. The cytoplasm contains proteins. Proteins are enzymes, which can be denatured by high temperatures. Most of the protein molecules in the cytoplasm float in the phospholipid layers. Some of the proteins are embedded in the outer layer; some in the inner layer and some span the whole membrane. They stay in the membrane because they have hydrophobic portions (made from hydrophobic amino acids), which sit among the hydrophobic phospholipid tails. Hydrophilic portions (made from hydrophilic amino acids) face out wards.

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*N.B.  Information in the prior knowledge was obtained from biology notes, s-cool website, biology 1 and experimental work in biology by D G mackean.

Prediction:-

I predict that the higher the temperature of water the more the red dye anthocyanin will be released from the beetroot. I think that this is because of the proteins in the cytoplasm. Proteins like all other enzymes are denatured at high temperatures. Most enzymes denature at temperatures above 50 degrees Celsius.  When the proteins are denatured the phospholipid layer of the cell membrane alters and has gaps in ...

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