Explain how you would test for the presence of lipids and proteins in an unknown solution. Give details on any observations you would expect to make.

To test for the presence of lipids, you would carry out the emulsion test. To do this, you take the sample and mix it with equal volumes of ethanol and water followed by shaking. A cloudy white emulsion will form if lipids are present. If lipids are absent, no emulsion will form.
To test for the presence of proteins, the biuret test should be carried out. To do this, a few drops of biuret reagent should be added. A blue to purple colour change will be observed if a protein is present. The higher the concentration of protein, the darker the purple colourisation will occur. If protein is not present, the sample solution will remain the colour of the biuret reagent, blue.