Practical Skills

Question 1

How does Biuret Test test for proteins?

Answer 1

Biuret Test tests for peptide bonds. Nitrogen atoms in the polypeptide chain can form a violet complex with Cu2+ ions in dilute Cu2+ sulphate in alkaline solution.

Question 2

What happens if Biuret Test is performed on proteins denatured by heat?

Answer 2

Yield positive result.
Peptide bonds are not broken during denaturation, only weak non covalent bonds like H bonds, ionic bonds, hydrophobic interactions etc.

Question 3

Benefits of simple dilution over serial dilution?

Answer 3

1. Each sample uses a fresh stock and distilled water -> errors will not be carried forward like in serial dilution
2. Allows narrower range of conc. to be easily obtained -> results obtained will be closer to the true value