The helical structure of protein is stabilised by:

Options

A. glycosidic bonds
B. dipeptide bonds
C. hydrogen bonds
D. all of these

Answer

To determine what stabilizes the helical structure of proteins, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Protein Structure**:
- Proteins have different levels of structure: primary, secondary, tertiary, and quaternary. The secondary structure includes alpha helices and beta sheets.

2. **Identifying the Helical Structure**:
- The alpha helix is a common secondary structure of proteins. It is characterized by a coiled shape.

3. **Role of Hydrogen Bonds**:
- The stability of the alpha helix is primarily due to hydrogen bonds. These bonds form between the carbonyl oxygen (C=O) of one amino acid and the amide hydrogen (N-H) of another amino acid that is four residues earlier in the sequence.

4. **Formation of Hydrogen Bonds**:
- In an alpha helix, the carbonyl oxygen atom points in one direction while the amide hydrogen points in the opposite direction. This arrangement allows for the formation of hydrogen bonds, which are crucial for maintaining the helical structure.

5. **Conclusion**:
- Therefore, the helical structure of proteins is stabilized by hydrogen bonds.

### Final Answer:
The helical structure of protein is stabilized by **hydrogen bonds**.

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