Question

2.20 unit 2: biochemistry summative test
you are testing for protein in a food sample, what color is a positive test for protein?
yellow
dark blue
purple/violet
red

Explanation:

When testing for protein using the Biuret test, the presence of protein (peptide bonds) causes a color change. The Biuret reagent (copper sulfate in alkaline solution) reacts with peptide bonds. In a positive test, the color changes to purple/violet due to the formation of a copper - peptide bond complex. Yellow is not a typical color for protein tests. Dark blue is not the color for a positive protein test in the Biuret test. Red is also not the color associated with a positive Biuret test for protein.

Answer:

purple/violet