The primary structure of a protein is due to :

Options

A. hydrogen bonds
B. peptide bonds
C. `-` S -S-linkages
D. ionic bonds

Explanation

To answer the question "The primary structure of a protein is due to:", we need to understand what the primary structure of a protein entails and how it is formed.

### Step-by-Step Solution:

1. **Definition of Primary Structure**:
The primary structure of a protein refers to the specific sequence of amino acids in a polypeptide chain. This sequence is unique for each protein and determines its overall structure and function.

2. **Formation of the Polypeptide Chain**:
Amino acids are linked together to form a polypeptide chain through a process called translation. Each amino acid is connected to the next by a type of covalent bond known as a peptide bond.

3. **Peptide Bonds**:
A peptide bond is formed between the carboxyl group of one amino acid and the amino group of another. This reaction results in the release of a molecule of water (condensation reaction) and creates a strong bond that holds the amino acids together in a linear sequence.

4. **Linear Structure**:
The primary structure is linear, meaning it does not have any folding or three-dimensional shape. It is simply a straight chain of amino acids linked by peptide bonds.

5. **Conclusion**:
Therefore, the primary structure of a protein is primarily due to the formation of peptide bonds between amino acids. Other types of bonds, such as hydrogen bonds, ionic bonds, and disulfide linkages, contribute to higher levels of protein structure (secondary, tertiary, and quaternary), but they do not play a role in the primary structure.

### Final Answer:
The primary structure of a protein is due to peptide bonds.

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