On analysis of a protein chain , it was found that it is made up of just a peptide bond. The possible structure of the protein is its

Options

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

Answer

To solve the question regarding the structure of a protein that is made up of just a peptide bond, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Peptide Bonds**:
- A peptide bond is a covalent bond formed between two amino acids. It occurs when the carboxyl group of one amino acid reacts with the amino group of another, releasing a molecule of water (a process known as dehydration synthesis).
- Proteins are polymers made up of amino acids linked by peptide bonds.

2. **Identifying Protein Structures**:
- Proteins have four levels of structure: primary, secondary, tertiary, and quaternary.
- **Primary Structure**: This is the linear sequence of amino acids in a polypeptide chain, held together by peptide bonds.
- **Secondary Structure**: This involves the folding or coiling of the polypeptide chain into structures such as alpha-helices or beta-pleated sheets, stabilized by hydrogen bonds.
- **Tertiary Structure**: This is the three-dimensional shape of a single polypeptide chain, formed by interactions between the side chains (R groups) of the amino acids.
- **Quaternary Structure**: This structure forms when two or more polypeptide chains come together to form a functional protein.

3. **Analyzing the Given Information**:
- The question states that the protein chain is made up of just a peptide bond. This indicates that we are dealing with a single linear sequence of amino acids, as there is no mention of folding or multiple chains.

4. **Conclusion**:
- Since the protein chain consists of only a single sequence of amino acids linked by peptide bonds, it can only represent the primary structure of the protein.

### Final Answer:
The possible structure of the protein is its **primary structure** (Option A).

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