Biuret Calibration Curve Linearity

Steps:

• Biuret reagent reacts with peptide bonds in proteins to produce purple color; absorbance measured at 540 nm.
• Calibration curve graphs absorbance (y-axis) vs. known protein concentrations (x-axis) for quantification.
• In colorimetry, Beer's Law dictates linear relationship between absorbance and concentration in dilute solutions.
• For protein hydrolysis monitoring, curve must be linear to accurately determine decreasing protein levels over time.

Why B is correct:

• B shows linear increase in absorbance with protein concentration, matching Beer's Law for biuret assay.

Why the others are wrong:

• A: Curved line violates linearity assumption of Beer's Law.
• C: Decreasing slope incorrect; absorbance rises with concentration.
• D: Non-linear or scattered points unfit for reliable calibration.

Final answer: B