The alpha helices and beta sheets are the example of which level of protein organization

Options

A. (a) Primary structure
B. (b) Secondary structure
C. (c) Tertiary structure
D. (d) Quaternary structure.

Answer

To determine the level of protein organization that includes alpha helices and beta sheets, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Protein Structure Levels**: Proteins have four levels of organization: primary, secondary, tertiary, and quaternary. Each level describes a different aspect of protein structure.

2. **Identify Primary Structure**: The primary structure refers to the linear sequence of amino acids in a polypeptide chain. This is the most basic level of protein structure and does not include any folding or structural features like helices or sheets.

3. **Identify Secondary Structure**: The secondary structure is characterized by local folded structures that form within a polypeptide due to hydrogen bonding. The two main types of secondary structures are alpha helices and beta sheets.

4. **Differentiate Between Alpha Helices and Beta Sheets**:
- **Alpha Helices**: These are coiled structures formed by intramolecular hydrogen bonds between the carbonyl oxygen of one amino acid and the amide hydrogen of another amino acid in the same chain.
- **Beta Sheets**: These are formed by intermolecular hydrogen bonds between different polypeptide chains or between different parts of the same chain, arranged in a sheet-like formation.

5. **Identify Tertiary and Quaternary Structures**:
- The tertiary structure refers to the overall three-dimensional shape of a single polypeptide chain, which is stabilized by interactions among the side chains (R groups) of the amino acids.
- The quaternary structure involves the assembly of multiple polypeptide chains into a larger protein complex.

6. **Conclusion**: Since alpha helices and beta sheets are specifically examples of local structural features formed by hydrogen bonding, they are classified under the secondary structure of proteins.

### Final Answer:
Alpha helices and beta sheets are examples of the **secondary structure** of protein organization.

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