Which structure of proteins involve in denaturation?

Options

A. Primary structure
B. Secondary structure
C. Tertiary structure
D. Quaternary structure

Answer

To determine which structures of proteins are involved in denaturation, we need to understand what denaturation is and how it affects protein structures.

### Step-by-Step Solution:

1. **Understanding Denaturation**:
- Denaturation refers to the process where a protein loses its native structure due to the disruption of non-covalent interactions. This can occur due to changes in temperature, pH, or other environmental factors.

2. **Protein Structures**:
- Proteins have four levels of structure:
- **Primary Structure**: The sequence of amino acids in a polypeptide chain.
- **Secondary Structure**: Local folding of the polypeptide chain into structures like alpha-helices and beta-pleated sheets.
- **Tertiary Structure**: The overall three-dimensional shape of a single polypeptide chain, formed by the folding and interactions of secondary structures.
- **Quaternary Structure**: The arrangement of multiple polypeptide chains into a functional protein complex.

3. **Effects of Denaturation**:
- During denaturation, the secondary and tertiary structures are primarily affected. The hydrogen bonds, ionic bonds, and hydrophobic interactions that maintain these structures can be disrupted, leading to loss of function.
- The primary structure, which is the sequence of amino acids, remains intact because it is held together by covalent bonds (peptide bonds) that are not broken during denaturation.
- The quaternary structure may also remain intact if the individual polypeptide chains are not separated.

4. **Conclusion**:
- Based on the understanding of denaturation and the structures of proteins, we conclude that the secondary and tertiary structures are involved in denaturation. The primary structure remains intact, while the quaternary structure may or may not be affected depending on the conditions.

### Final Answer:
The structures of proteins involved in denaturation are the **secondary structure** and the **tertiary structure**.