Lab 5 Report: The Chemistry of Life

Experiment 1: Testing for Proteins
The protein molecules in many foods provide the amino acid building blocks required
by our own cells to produce new proteins. To determine whether a sample contains
protein, a reagent called Biuret solution is used. Biuret solution contains copper ions.
However, the chemical state of the copper ions in Biuret solution causes them to
form a chemical complex with the peptide bonds between amino acids (when
present), changing the color of the solution. Biuret solution is normally blue, but
changes to pink when short peptides are present and to violet when long
polypeptides are present.

Figure 6: Biuret solution only is located on the
far left side of the image (blue). Note the
transition from blue to violet as proteins are
added to the solution, causing the solution to
transition from blue to violet.

Materials
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(2) 250 mL Beakers
25 Drops Biuret Solution,
H2NC(O)NHC(O)NH
(1) Knox® Gelatin Packet
5 mL 1% Glucose Solution,
C6H12O6
(1) 10 mL Graduated Cylinder
(1) 100 mL Graduated Cylinder
Permanent Marker
5 Pipettes

5 Test Tubes (Plastic)
Test Tube Rack
5 mL Unknown Solution
*Tap Water
*Hot Water
*Egg White