2.1.2 (q) Qualitative tests

How would you test for lipids?

• Mix sample with water then ethanol.

• Mix sample with ethanol then water.

• Mix sample with Biurets.

• Mix sample with iodine.

What is the name of the cloudy layer seen in a test tube after a lipid sample is mixed with ethanol and water?

Lipids dissolve in what solvent?

• water

• ethanol

• both

• lipids are insoluble in all solvents

What colour changes would you expect if you mixed a sample containing protein with Benedict's solution?

• Blue to purple.

• Purple to blue.

• Blue to brick red.

• No change

What colour changes would you expect if you mixed a sample containing protein with Biuret solution?

• Blue to purple.

• Purple to blue.

• Blue to brick red.

• No change.

In a reducing sugars test, after adding Benedict's solution to the sample, what should you do?

• Add hydrochloric acid (HCl)

• Place test tube in boiling water bath

• Add sodium hydroxide

• Nothing - observe the changes.

Pick the reagent/s which is/are required to adapt the Benedict's test for non-reducing sugars.

• A digestive enzyme, eg trypsin

• A strong acid, eg HCl

• A strong alkaline, eg NaOH

• Boiling water bath