Immunoglobulins are proteins that show a structure

Options

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

Answer

### Step-by-Step Solution

1. **Understanding Immunoglobulins**:
- Immunoglobulins, also known as antibodies, are proteins that play a crucial role in the immune response. They help in identifying and neutralizing pathogens like bacteria and viruses.

2. **Structure of Immunoglobulins**:
- Immunoglobulins have a distinctive Y-shaped structure. This structure consists of two types of polypeptide chains: heavy chains and light chains.

3. **Chains in Immunoglobulins**:
- Each immunoglobulin molecule is made up of four polypeptide chains: two heavy chains and two light chains. The heavy chains are larger and provide the bulk of the antibody, while the light chains are smaller.

4. **Regions of Immunoglobulins**:
- The immunoglobulin structure can be divided into two main regions:
- **Variable Region**: This part of the antibody is responsible for binding to specific antigens. It varies among different antibodies.
- **Constant Region**: This part remains the same for all antibodies of a particular class and is involved in the immune response.

5. **Classification of Protein Structures**:
- Proteins can be classified into four structural levels:
- **Primary Structure**: The linear sequence of amino acids in a polypeptide chain.
- **Secondary Structure**: Local folding of the polypeptide chain into structures like alpha helices and beta sheets.
- **Tertiary Structure**: The overall three-dimensional shape of a single polypeptide chain.
- **Quaternary Structure**: The assembly of multiple polypeptide chains into a larger functional complex.

6. **Identifying the Structure of Immunoglobulins**:
- Given that immunoglobulins are composed of multiple polypeptide chains (two heavy and two light chains), they exhibit a quaternary structure. This structure is stabilized by disulfide bonds between the chains.

7. **Conclusion**:
- Therefore, the correct answer to the question is that immunoglobulins are proteins that show a **quaternary structure**.