The helical structure or a secondary structure of proteins is stabilised by

Options

A. peptide bonds
B. dipeptide bonds
C. H - bond
D. ether bonds

Explanation

To answer the question regarding the stabilization of the helical structure or secondary structure of proteins, we can break down the explanation step by step.

### Step-by-Step Solution:

1. **Understanding Protein Structure**:
- Proteins are made up of amino acids linked together by peptide bonds. The sequence and interactions of these amino acids lead to various levels of protein structure: primary, secondary, tertiary, and quaternary.

2. **Identifying Secondary Structure**:
- The secondary structure of proteins refers to local folded structures that form within a polypeptide due to interactions between the backbone atoms. The most common types of secondary structures are alpha-helices and beta-pleated sheets.

3. **Role of Peptide Bonds**:
- Peptide bonds are covalent bonds that link the amino group of one amino acid to the carboxyl group of another. While these bonds are crucial for forming the primary structure, they also play a role in the secondary structure.

4. **Formation of Hydrogen Bonds**:
- In an alpha-helix, the carbonyl oxygen (C=O) of one amino acid forms a hydrogen bond with the amide hydrogen (N-H) of another amino acid that is typically four residues earlier in the sequence. This interaction is crucial for stabilizing the helical structure.

5. **Conclusion**:
- Therefore, the helical structure or secondary structure of proteins is stabilized primarily by hydrogen bonds formed between the carbonyl oxygen of one amino acid and the amide hydrogen of another.

### Final Answer:
The helical structure or secondary structure of proteins is stabilized by **hydrogen bonds**.

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