The structure of a protein is determined by :

Options

A. electrostatic bonding
B. amino acid sequence
C. amino acid composition
D. hydrophobic bonding

Explanation

To determine how the structure of a protein is established, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Protein Composition**:
- Proteins are made up of smaller units called amino acids. There are 20 different amino acids that can combine in various sequences to form proteins.

2. **Role of Amino Acid Sequence**:
- The specific order of amino acids in a protein is known as its amino acid sequence. This sequence is crucial because it dictates how the protein will fold and function.

3. **Peptide Bond Formation**:
- Amino acids are linked together by peptide bonds. This bond forms through a dehydration reaction, where a water molecule is removed as two amino acids combine.

4. **Levels of Protein Structure**:
- **Primary Structure**: This is the linear sequence of amino acids in a polypeptide chain.
- **Secondary Structure**: This involves the folding or coiling of the polypeptide chain into structures such as alpha helices and beta sheets due to hydrogen bonding.
- **Tertiary Structure**: This is the overall three-dimensional shape of a single polypeptide chain, formed by further folding and interactions among R groups (side chains) of amino acids.
- **Quaternary Structure**: This structure arises when two or more polypeptide chains come together to form a functional protein.

5. **Conclusion**:
- The structure of a protein is primarily determined by its amino acid sequence. This sequence influences all subsequent levels of protein structure, from primary to quaternary.

### Final Answer:
The structure of a protein is determined by the **amino acid sequence**.

---