Amino Acids

The correct option is (C): A, B, C, D only

To correctly match List-I (Amino Acids) with List-II (Nature of Amino Acid), we must first understand the properties of each amino acid.

Based on these properties, we can match each amino acid with its correct nature:

This alignment matches the given correct answer: (A) - (II), (B) - (IV), (C) - (I), (D) - (III).

The question requires identifying an essential amino acid from the given options. Essential amino acids are those that cannot be synthesized by the human body and must be obtained from the diet. Here's a breakdown to understand which among the given amino acids is essential:

Thus, the correct answer is Valine, as it is classified as an essential amino acid.

Step 1: Understanding the -helix structure.
The -helix structure in proteins is stabilized primarily by hydrogen bonds (H-bonds) between the backbone amide and carbonyl groups of the protein’s polypeptide chain.
Step 2: Analyzing the options.
- Ionic bond: Ionic bonds are not typically involved in stabilizing the -helix structure.
- Covalent interaction: While covalent bonds are important in proteins, they are not the primary stabilizing forces in the -helix.
- H-bond: Hydrogen bonds are the main interactions stabilizing the -helix. - Banana bond: This is not a valid type of bond in protein structure.
Step 3: Conclusion.
The correct interaction that stabilizes the -helix is the hydrogen bond (H-bond).
Final Answer: