Peptide linkage is

Options

A. `COHN_(2)`
B. `-CO.NH`
C. `-COONH_(2)`
D. `-CH-NH`

Answer

### Step-by-Step Solution:

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

2. **Formation of Peptide Linkage**:
- A peptide linkage (or bond) is formed between two amino acids. This occurs through a dehydration synthesis reaction, where a water molecule (H2O) is removed.

3. **Dehydration Synthesis**:
- In this reaction, the amino group (NH2) of one amino acid reacts with the carboxyl group (COOH) of another amino acid.
- The reaction can be represented as:
\[ \text{Amino Acid 1 (NH2-R1)} + \text{Amino Acid 2 (NH2-R2)} \rightarrow \text{Dipeptide (R1-CO-NH-R2)} + H2O \]

4. **Representation of the Peptide Bond**:
- The resulting bond between the carbon atom of the carboxyl group of the first amino acid and the nitrogen atom of the amino group of the second amino acid is called the peptide bond.
- This bond can be represented as:
\[ -C(=O)-N-H- \]
- In a simplified form, it is often represented as C-O-N-H.

5. **Conclusion**:
- The peptide linkage is essential for forming proteins, as it connects amino acids in a chain, leading to the formation of polypeptides and ultimately proteins.