`beta` pleated structure of a molecule can be seen in the following level of protein

Options

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

Answer

To answer the question regarding the presence of the beta pleated structure in proteins, we need to analyze the different levels of protein structure: primary, secondary, tertiary, and quaternary.

### Step-by-Step Solution:

1. **Understanding Protein Structure Levels**:
- **Primary Structure**: This is the linear sequence of amino acids in a polypeptide chain, held together by peptide bonds. There are no secondary structures like beta pleated sheets at this level.
- **Secondary Structure**: This level involves the folding of the polypeptide chain into structures such as alpha helices and beta pleated sheets. The beta pleated sheet is a common secondary structure formed by hydrogen bonds between the backbone atoms in different strands of the polypeptide.
- **Tertiary Structure**: This structure refers to the overall three-dimensional shape of a single polypeptide chain, which is stabilized by various interactions, including hydrogen bonds, ionic bonds, and disulfide bridges. It does not specifically include beta pleated sheets as a defining feature.
- **Quaternary Structure**: This level involves the assembly of multiple polypeptide chains into a larger complex. While quaternary structures can contain beta pleated sheets, they are not defined by them.

2. **Identifying the Correct Answer**:
- Since the question specifically asks for the level of protein structure where beta pleated sheets can be found, the correct answer is the **secondary structure**. This is where the beta pleated sheet is prominently featured due to the hydrogen bonding between different segments of the polypeptide chain.

### Conclusion:
The beta pleated structure of a molecule can be seen in the **secondary level of protein structure**.

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