The effect of temperature on the loss of red dye from beetroot cells.

Laura Wallace

The effect of temperature on the loss of red dye from beetroot cells

Interpretation of results:

The cell membrane functions as a semi-permeable barrier, its function is to isolate the inside of the cell from its environment, allowing a very few molecules through it while keeping the majority of chemicals inside the cell. All cells have membranes, the beetroot membrane is made up of phospholipids, these phospholipids are arranged on the membrane along with the intrinsic and extrinsic proteins.

Each phospholipid consists of a hydrophobic tail of 2 fatty acids and hydrophilic phosphate head. These phospholipids are aligned tail to tail so the hydrophobic tails point inwards and have no contact with water, where as the hydrophilic heads on the inner and outer surface of the membrane has contact with water. The intrinsic proteins act as carriers across the membrane and as passive routes for movements in and out of the cell.

This diagram shows the arrangement of the plasma membrane:

In the cells of a beetroot plant, anthocyanin is the substance contained within the plasma membrane, it is this, which gives the beetroot its characteristic red colour. If a cell is damaged in a beetroot plant and the membrane is broken, the anthocyanin 'bleeds' from the cells like a dye. An increase in temperature will damage and denature the plasma membrane and cause the cytoplasm and other substances contained within the membrane to leak out. Beetroots red pigment, anthocyanin, cannot pass through the intact cell membrane.

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As temperature increase more energy is made making more successful collision between water molecules and the beetroot cells, which will be damaging the beetroot membrane causing a leakage of dye. Also like all proteins the proteins in the phospholipid bi-layer denature at higher temperatures. Also as the membrane heats up, the phospholipid bi-layer becomes more fluid at higher temperatures and large gaps appear in it and so the pigment can escape.

Proteins are made up of the tertiary structures which is a three dimensional shape. The bonds holding it together are hydrogen bonds when these bonds are broken down by heat energy it is know as denaturation, and so the tertiary protein loses its specific shape this process is irreversible

The colour intensity of a red solution is proportional to the amount of red pigment diffused out which, in turn, is proportional to the number of cells damaged of the cell membrane.

Trends and patterns:

As temperature increased transmission decreased, this showed evidence that more dye is lost from the cells at high temperature this was due to the damage high temperature have on the plasma membrane as the proteins are denatured and there fore allows dye out of the cells, the higher the temperature the higher amount of denatured enzymes.

At 0’c there was high transmission meaning little if any dye was lost, this is because the plasma membrane is not affected as the proteins are still intact and are concealing the dye, there is little energy within the water molecules to damage the membrane.

There is little damaged done to the membrane up to 40’C, after 40’C the proteins became denatured and dye was lost, this is due to the loss of the tertiary shaped protein as hydrogen bonds were broken after 4o’C.

Evaluation

The plan gave no indication of the time the beetroot cells should have been left in there temperature, this could have had great effect on the results, as little time in the baths would of meant there was low energy made and so reaction would have been very slow, left in to long would of damaged the cells causing and inaccurate transmission of the dye lost at each temperature.

There was also no reference as to the amount of water the cells should of been left in over night and more importantly the amount in which they were heated up. A small amount of water would of meant either the beetroot slice was not fully submerged, causing and inaccurate recording of the dye lost at that temperature and too much water would of shown little transmission as the concentration of water molecules would have been so much greater than the amount of dye molecules lost.

Lack of repetition gave an inaccurate average recording for each temperature, by increasing repetition a more accurate average could have been formed for each temperature.

Anonymous results:

I have highlighted the anonymous result in red on the results table.

In column A it shows 0’c having a lower transmission than at 10’C and 20’c which showed 100 % transmission (clear) although there should have been little difference the other beetroot columns showed a steady decrease in transmission, except column C which showed transmission of 95 % for 0’c, which other columns showed at 40’c when the proteins were becoming denatured.

Column D had a very little transmission at 70’c at just 3% unlike the others which were between 12 and 18 %, this brought the average transmission for 70’c down, this could of been that it was left in the high temperature for longer and so more proteins were denatured and more dye had been lost causing a low transmission.

The main limitation was the lack of repetitions as more repetitions would of given a more accurate transmission recording for each temperature, and there fore would have been more reliable.

To improve this experiment I would of increased repetitions for each temperature and had a wider range of temperature to experiment with.

These results are representative as I expected them knowing that up to 40’c there was little dye lost, after 40’c an increase in dye was lost, this was due to the proteins becoming denatured above 40’c as hydrogen bonds are broken in the tertiary shape of the protein and so dye was able to leak out.