Learning Path
Question & Answer1
Understand Question2
Review Options3
Learn Explanation4
Explore TopicChoose the Best Answer
A
Add Biuret reagent to the protein solution.
B
Measure the absorbance at 540 nm.
C
Prepare a standard curve using known protein concentrations.
D
Incubate the reaction mixture at room temperature.
Understanding the Answer
Let's break down why this is correct
Answer
To measure protein concentration with the Biuret method, first place the protein sample in a cuvette (step A). Next, add the Biuret reagent, which contains potassium hydroxide and sodium hydroxide (step B). Then add copper sulfate solution, which reacts with peptide bonds to form a violet complex (step C). Finally, read the absorbance at 540 nm with a spectrophotometer and compare it to a standard curve (step D). This sequence ensures the copper ions bind only to proteins, giving a measurable color change proportional to protein amount.
Detailed Explanation
First, a standard curve is made so we know how absorbance relates to protein amount. Other options are incorrect because Adding the reagent first skips the standard curve, so we have no reference for the unknown sample; Measuring absorbance before the color has time to form gives a low reading.
Key Concepts
Protein Measurement Techniques
Biuret Method for Protein Quantification
Spectrophotometry
Topic
Protein Measurement Methods
Difficulty
hard level question
Cognitive Level
understand
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