NURSING EXAM QUESTIONS
BIOCHEMISTRY
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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What color changes the biuret reacton in the presence of NaOH and sodium-potassium tetrate?
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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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Explanation:
Detailed explanation-1: -In the presence of alkaline, when Biuret is reacted with dilute copper sulphate, a purple coloured substance is formed. The reason behind this colour is the formation of a chelate complex or the copper coordination complex.
Detailed explanation-2: -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-3: -Sodium hydroxide provide the alkaline medium and potassium sodium tartrate is added to chelate and thus stabilize the cupric ions in the solution or to maintain their solubility in alkaline solution. The copper (II) present in the reaction binds itself to the nitrogen atoms that are present in the protein peptides.
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