Quaternary structure is found in

Options

A. Simple monomeric proteins
B. Conjugate monomeric proteins
C. Oligoproteins
D. Both B and C.

Answer

### Step-by-Step Solution:

1. **Understanding Quaternary Structure**:
- The quaternary structure of a protein refers to the arrangement and interaction of multiple polypeptide chains (subunits) in a protein complex. It is the highest level of protein structure.

2. **Identifying Protein Types**:
- There are different types of proteins based on their structure:
- **Monomeric Proteins**: These consist of a single polypeptide chain and do not exhibit quaternary structure.
- **Conjugate Monomeric Proteins**: These are proteins that contain a non-polypeptide component but still do not have a quaternary structure.
- **Oligoproteins**: These are proteins made up of two or more polypeptide chains. They exhibit quaternary structure due to the interaction between these chains.

3. **Examples of Proteins with Quaternary Structure**:
- Some well-known proteins that exhibit quaternary structure include hemoglobin, DNA polymerase, and ion channels. These proteins consist of multiple subunits that work together.

4. **Stabilization of Quaternary Structure**:
- The quaternary structure is stabilized by various types of bonds, including hydrogen bonds, disulfide bridges, and salt bridges. These interactions help maintain the overall shape and function of the protein.

5. **Evaluating the Options**:
- **Option A (Simple Monomeric Proteins)**: Incorrect, as these do not have a quaternary structure.
- **Option B (Conjugate Monomeric Proteins)**: Incorrect, as these also do not exhibit quaternary structure.
- **Option C (Oligoproteins)**: Correct, as these proteins do have quaternary structure.
- **Option D (Both B and C)**: Incorrect, since only C is correct.

6. **Conclusion**:
- The correct answer to the question "Quaternary structure is found in" is **Option C: Oligoproteins**.