A peptide bond is formed when `NH_(2)` group combines with

Options

A. COOH group
B. hydrogen group
C. `CH_(2)` group
D. another `NH_(2)` group

Answer

To determine what a peptide bond is formed from, we need to understand the components involved in its formation:

1. **Understanding Peptide Bonds**: A peptide bond is a type of covalent bond that links two amino acids together. It is crucial in the structure of proteins.

2. **Components of Amino Acids**: Each amino acid consists of an amino group (NH₂), a carboxylic group (COOH), a hydrogen atom, and a variable side chain (R group).

3. **Formation of a Peptide Bond**: The formation of a peptide bond occurs through a condensation reaction, where two amino acids combine. Specifically, the amino group of one amino acid reacts with the carboxylic group of another amino acid.

4. **Reaction Details**:
- The carboxylic group (COOH) of one amino acid loses an OH (hydroxyl group).
- The amino group (NH₂) of the other amino acid loses an H (hydrogen atom).
- This loss results in the release of a water molecule (H₂O) and the formation of a peptide bond (C(=O)NH).

5. **Identifying the Correct Answer**: Given the options:
- Carboxylic group
- Hydrogen group
- CH₂ group
- Other amino group

The correct answer is the **carboxylic group**, as it is the component that combines with the amino group to form the peptide bond.

### Final Answer:
A peptide bond is formed when the NH₂ group combines with the **carboxylic group**.

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