Each polypeptide in a protein has amino acids linked with each other in a specific sequence. This sequence of amino acids is said to be... .

Options

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

Answer

To answer the question, "Each polypeptide in a protein has amino acids linked with each other in a specific sequence. This sequence of amino acids is said to be...", we need to identify the term that describes this specific sequence of amino acids in a polypeptide chain.

### Step-by-Step Solution:

1. **Understanding Polypeptides**:
- A polypeptide is a long chain of amino acids linked together by peptide bonds. These chains can vary in length and composition.

2. **Defining Protein Structure**:
- Proteins are made up of one or more polypeptides that fold into specific shapes. The structure of proteins can be categorized into four levels: primary, secondary, tertiary, and quaternary.

3. **Identifying the Primary Structure**:
- The primary structure of a protein refers specifically to the sequence of amino acids in a polypeptide chain. This sequence is crucial because it determines the protein's unique characteristics and functions.

4. **Importance of Peptide Bonds**:
- The amino acids in the polypeptide chain are linked by peptide bonds, which are formed during protein biosynthesis. This linkage is essential for maintaining the integrity of the primary structure.

5. **Conclusion**:
- Therefore, the specific sequence of amino acids in a polypeptide chain is referred to as the **primary structure** of the protein.

### Final Answer:
The sequence of amino acids in a polypeptide chain is said to be the **primary structure** of the protein.

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