Introduction

Amino acids are the building blocks of proteins and play a crucial role in various biological functions. Understanding the properties of these amino acids, particularly under physiological conditions (around pH 7.4), helps us understand their behavior in biological systems. In this article, we’ll match Leucine, Lysine, Glutamic acid, and Glutamine to their correct properties at physiological pH.

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The Question Breakdown:

Q10:
In physiological conditions, match the components of List I with those in List II.

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Understanding the Properties of Amino Acids

1. Leucine (A)

   • Non-polar amino acid with a hydrophobic side chain.

   • Properties at physiological pH: It is non-polar, meaning it does not interact with water and is typically found in the interior of proteins.

   • Correct Match: II – Non-polar

2. Lysine (B)

   • Positively charged amino acid with an amino group (–NH₃⁺) on the side chain.

   • Properties at physiological pH: At pH 7.4, the amino group is protonated and carries a positive charge.

   • Correct Match: IV – Positively charged

3. Glutamic Acid (C)

   • Negatively charged amino acid with a carboxyl group (–COO⁻) on the side chain.

   • Properties at physiological pH: The carboxyl group dissociates, making glutamic acid negatively charged at physiological pH.

   • Correct Match: I – Negatively charged

4. Glutamine (D)

   • Uncharged polar amino acid with an amide group (–CONH₂) on the side chain.

   • Properties at physiological pH: Although it is polar due to the amide group, it is uncharged.

   • Correct Match: III – Uncharged polar

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Final Matching Summary

• A – II: Leucine is non-polar.

• B – IV: Lysine is positively charged.

• C – I: Glutamic acid is negatively charged.

• D – III: Glutamine is uncharged polar.

Correct Answer: (b) A – II, B – IV, C – I, D – III

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Conclusion

Understanding amino acid properties is essential for grasping how proteins fold, interact, and function in biological systems. At physiological pH, the charge and polarity of amino acids determine their behavior and their role in various biochemical processes. By knowing how amino acids like Leucine, Lysine, Glutamic acid, and Glutamine interact, we gain insights into their essential roles in enzymes, signaling molecules, and structural proteins.