The first amino acid in the primary structure of the Protein is placed in

Options

A. right end
B. left end
C. middle
D. right end and left end

Answer

To determine where the first amino acid in the primary structure of a protein is placed, we need to understand the structure of amino acids and how they are linked together to form proteins.

### Step-by-Step Solution:

1. **Understanding Amino Acids**: Amino acids are the building blocks of proteins. Each amino acid has a central carbon atom (alpha carbon) bonded to four different groups: an amino group (NH2), a carboxyl group (COOH), a hydrogen atom (H), and a variable R group (side chain).

2. **Primary Structure of Proteins**: The primary structure of a protein refers to the linear sequence of amino acids linked together by peptide bonds. This sequence is crucial as it determines the protein's overall structure and function.

3. **Directionality of Protein Chains**: Proteins have a specific directionality. The end of the protein chain that has a free amino group (NH2) is referred to as the N-terminal (or amino terminus). The end that has a free carboxyl group (COOH) is referred to as the C-terminal (or carboxyl terminus).

4. **Placement of the First Amino Acid**: When proteins are synthesized, the first amino acid added to the growing polypeptide chain is placed at the N-terminal end. This means that the first amino acid is located at the left end of the protein chain.

5. **Conclusion**: Therefore, the first amino acid in the primary structure of the protein is placed at the left end, which corresponds to the N-terminal side.

### Final Answer:
The first amino acid in the primary structure of the protein is placed at the **left end** (N-terminal).

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