The alpha helix in a protein is classified as the

Options

A. tertiary structure
B. secondary structure
C. primary structure
D. quaternary structure

Explanation

To solve the question regarding the classification of the alpha helix in a protein, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Protein Structure**: Proteins have different levels of structure, which include primary, secondary, tertiary, and quaternary structures. Each level represents a different aspect of protein organization.

2. **Identifying the Alpha Helix**: The alpha helix is a specific type of structural arrangement within proteins. It is characterized by a coiled or spiral shape.

3. **Classifying the Alpha Helix**: The alpha helix is classified as a secondary structure of proteins. This is because secondary structures are formed by the folding and coiling of the polypeptide chain, stabilized by hydrogen bonds.

4. **Differentiating Between Structures**:
- **Primary Structure**: The sequence of amino acids in a polypeptide chain.
- **Secondary Structure**: Includes structures like alpha helices and beta sheets, which are formed by hydrogen bonding between backbone atoms.
- **Tertiary Structure**: The overall three-dimensional shape of a single polypeptide chain.
- **Quaternary Structure**: The arrangement of multiple polypeptide chains in a multi-subunit complex.

5. **Conclusion**: Since the alpha helix is specifically a type of secondary structure, the correct answer to the question is **option B: secondary structure**.