Mawawalfor Gerneral oranic and Biological D. Color Tests for Proteins Observatio
ID: 501982 • Letter: M
Question
Mawawalfor Gerneral oranic and Biological D. Color Tests for Proteins Observations of Color Tests 1. Biuret 2. Ninhydrin 3. Sample ant Glycine Tyrosine Gelatin Egg albumin Casein (milk protein) Questions and Problems Q5 After with HNO3, a student noticed that she had a yellow spot on her hand. What might be the reason? Q6 Which samples give a negative biuret test? Why? Q7 What functional group gives a positive test in the xanthoproteic test? Q8 What tests could you use to determine whether an unlabeled test tube contained an amino acid or a protein?Explanation / Answer
Q5. Yellow spot on hand is a result of Xanthoprotein reaction.Amino acis on the skin reacts with concentated HNO3 to form yellow colour.
Q6. Only Glycine, gives -ve biuret test because Biuret test is used to detect peptide bonds.Glycine being free amino acid does not have any peptide bonds
Q7. Tyrosine, Gelatin, Egg albumin, casein will give +ve test in Xanthoproteic test.
Q8. Biuret test is used because +ve result indicates presence of proteins with 2 or more peptide bonds. If such a protein is not present blue colour of cupric sulphate will remain.