OBJECTIVE LIFE SCIENCE
BIOCHEMISTRY
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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From blue to brown
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From blue to green
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From blue to red
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From blue to purple
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Detailed explanation-1: -The reagent contains copper ions that react with peptide bonds in proteins, resulting in the formation of a complex that absorbs light at a wavelength of around 540 nm, which causes the blue solution to change color to violet or pink.
Detailed explanation-2: -Biuret solution is a blue liquid that changes to purple color when it reacts with proteins present in food. Biuret solution is made by mixing copper sulfate with sodium hydroxide. Copper sulfate gives a typical blue color to this solution, which is turned to purple after reacting with the proteins.
Detailed explanation-3: -A positive test is indicated by: a deep blue/purple color due to the copper ion complex with the amide group of the protein.
Detailed explanation-4: -Cu (II) or cupric ions create a chelate complex of violet colour, using oxygen of water and the unshared electron pairs of peptide nitrogen. Since this complex absorbs light in 540 nm, it appears violet. In the presence of protein, it changes its colour from blue to violet.
Detailed explanation-5: -The reagent used in the Biuret Test is a solution of copper sulfate (CuSO4) and sodium hydroxide (NaOH). The NaOH is there to raise the pH of the solution to alkaline levels; the crucial component is the copper II ion (Cu2+) from the CuSO4.