Question

Given below are two statements: 
Statement I: Arginine and Tryptophan are essential amino acids. 
Statement II: Glycine does not have any chiral carbon. 
In the light of the above statements, which is the correct option?

• A. Both statement-I and statement-II are correct
• B. Both statement-I and statement-II are incorrect
• C. Statement-I is correct and statement-II is incorrect
• D. Statement-I is incorrect and statement-II is correct

Hint:

Important facts about amino acids: \begin{itemize} \item Glycine is the only amino acid without a chiral carbon \item Essential amino acids must be obtained from diet \item Arginine is conditionally essential \end{itemize}

Answer 1

The Correct Option is D

To determine the correctness of the given statements, let's analyze each statement separately based on known chemical facts about amino acids.

1. Statement I: Arginine and Tryptophan are essential amino acids.
   • Essential amino acids are those that cannot be synthesized by the body and must be obtained from the diet. The common essential amino acids include:
     • Histidine
     • Isoleucine
     • Leucine
     • Lysine
     • Methionine
     • Phenylalanine
     • Threonine
     • Tryptophan
     • Valine
   • From the list above, we can see that Tryptophan is indeed an essential amino acid.
   • Arginine is considered conditionally essential, which means it is normally synthesized by the body, but under certain conditions (such as in young children, recovering patients, or during specific illnesses), it might need to be obtained from the diet.
   • Hence, this statement is incorrect as it inaccurately classifies Arginine as an essential amino acid.
2. Statement II: Glycine does not have any chiral carbon.
   • A chiral carbon is a carbon atom that is attached to four different atoms or groups. This property makes the molecule chiral, and it can exist as non-superimposable mirror images.
   • Glycine is the simplest amino acid with the structure NH₂-CH₂-COOH. In Glycine, the central carbon atom is bonded to two hydrogen atoms, the amine group, and the carboxylate group.
   • Because its central carbon is bonded to two identical hydrogen atoms, Glycine lacks a chiral center, making it the only amino acid without a chiral carbon.
   • Therefore, this statement is correct.

Based on the analysis above, the correct answer is: Statement-I is incorrect and statement-II is correct.