Which type of bonding is present in `alpha`-helix structure to stabilise it ?

Options

A. ionic bonding
B. C-C covalent bonding
C. Hydrogen bonding
D. N-N covalent bonding

Answer

To determine the type of bonding that stabilizes the alpha-helix structure in 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 alpha-helix is a type of secondary structure.

2. **Identifying Types of Bonds**:
- There are several types of bonds that can be present in proteins, including ionic bonds, covalent bonds, and hydrogen bonds.

3. **Evaluating Ionic Bonds**:
- Ionic bonds are formed between charged ions. In the context of the alpha-helix structure, ionic bonds do not play a significant role in stabilizing the helical shape.

4. **Evaluating Covalent Bonds**:
- Covalent bonds, such as carbon-carbon or nitrogen-nitrogen bonds, involve the sharing of electrons. While covalent bonds are essential for the overall structure of proteins, they do not specifically stabilize the alpha-helix.

5. **Evaluating Hydrogen Bonds**:
- Hydrogen bonds occur when a hydrogen atom covalently bonded to an electronegative atom (like oxygen or nitrogen) interacts with another electronegative atom. In the alpha-helix, hydrogen bonds form between the carbonyl oxygen (C=O) of one amino acid and the amide hydrogen (N-H) of another amino acid four residues down the chain.

6. **Conclusion**:
- The primary stabilizing force in the alpha-helix structure is hydrogen bonding. These bonds help maintain the helical shape by linking different parts of the polypeptide chain together.

### Final Answer:
The type of bonding that stabilizes the alpha-helix structure is **hydrogen bonding**.

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