Testing and Evaluating the Contents of Two Known Solutions for Proteins and Lipids
For this experiment two solutions will be provided. In one test tube
it contains milk and in the other test tube it contains sunflower oil.
The test for proteins and lipids will be done for each solution and
then a conclusion can be deduced from these results.
To test for the proteins place 2cm³ of the test solution into a test
tube and then add five drops of the Biuret solution to it. It is
important to known what it is your looking for , in this case to show
that there are proteins present it should develop a purple- violet
colour, the intensity of which is proportional to the content of
protein, with a high content of protein it will give a darker
precipitate rather than if it had a low content where the precipitate
will be lighter in colour. However if in doubt about the colour add
more drops to it , wait a few moments a purple colour will develop if
a protein is present. The reason why there is this colour change is
because in because of the nitrogen atoms in the Biuret solution
present in the peptide chain form a purple complex ( the nitrogen)
with the Cu ²+ ions, it is the dilute copper sulphate that is in an
For the test for lipids I can use two tests. The first test being the
translucence test where a drop of each solution is put on a piece of
filter paper, if lipids is present than it should turn the filter
paper translucent this because of the oils in the triglyceride chains
causes this translucent effect on the filter paper.
However if this test proves unsuccessful and not clear another test
can be done this is the emulsion test. This is to add 2cm³ of fat or
oil to a test tube containing 2cm³ of absolute ethanol, then add an
equal amount of water. It is important to know what should happen if
lipids are present and this is that a cloudy whit suspension should
appear and this is because lipids are immiscible when they are in
water. So when water is added to a solution of the lipid in alcohol
results in an emulsion of tiny lipid droplets which are in the water
reflect light and so therefore give a white , opalescent appearance.
The constituents found in milk are in a sample of 250ml is protein-8g
Of which are sugars 12g
Of which is saturated 6g
This is for a sample of milk 250ml that is full fat milk. Milk is made
up of 88% of water, tiny globules of fat float in it which is what
makes it an opaque rather than transparent liquid. The fats are mostly
triglycerides which provide a source of energy for the suckling
infant. The kinds of fatty acids in the triglycerides vary according
to the diet of the mother. Milk also contains the disaccharide...