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MCQEasyJEE 2023Proteins (Amino Acids, Structure, Denaturation)

JEE Chemistry 2023 Question with Solution

The naturally occurring amino acid that contains only one basic functional group in its chemical structure is:

  • A

    Histidine

  • B

    Lysine

  • C

    Aspartic acid

  • D

    Arginine

Answer

Correct answer:C

Step-by-step solution

Standard Method

Given: The amino acids listed are Histidine, Lysine, Aspartic acid, and Arginine.

Find: Which amino acid contains only one basic functional group in its chemical structure.

The solution is internally inconsistent with the question options. It states The Correct Option is D, but the explanatory text analyzes Asparagine, which is not present in the options. The answer key states (3) Aspartic acid, which also conflicts with the explanatory discussion.

From the extracted explanation:

  • Histidine has an imidazole group and an amino group, so it has more than one basic functional group.
  • Lysine has two amino groups, so it has more than one basic functional group.
  • Arginine has a guanidinium group and an amino group, so it has more than one basic functional group.
  • The explanation concludes that Asparagine has only one basic functional group, but Asparagine is not one of the listed options.

Therefore, the provided source material does not support a uniquely valid option among A–D for the question exactly as scraped. The answer is marked AMBIGUOUS due to mismatch between question, options, answer key, and the solution.

Common mistakes

  • Choosing Aspartic acid because its name resembles Asparagine. This is incorrect because these are different amino acids with different side chains. Always match the exact option name with the functional group discussed.

  • Counting only the side-chain basic group and ignoring the common amino group −NH2-\text{NH}_2. This leads to undercounting basic functional groups. Always include both the main amino group and any basic side-chain group.

  • Assuming the stated correct option letter must be right even when the explanation discusses a different compound. This is risky because provided solutions can contain mismatches. Verify the option against the actual functional-group analysis.

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