Which of the following statements regarding a peptide linkage in a protein molecule is/are correct ?

Options

A. It is an amide linkage
B. It has partial double bond character
C. It is hydrophilic in nature
D. It connects protein molecules through H - bonds

Explanation

To solve the question regarding the correctness of statements about peptide linkages in protein molecules, we can follow these steps:

### Step 1: Understand the Structure of Peptide Linkage
A peptide linkage (or bond) is formed between the carboxyl group of one amino acid and the amino group of another amino acid. This reaction results in the release of a water molecule (condensation reaction) and the formation of an amide bond.

### Step 2: Identify Key Characteristics of Peptide Linkages
1. **Amide Linkage**: Peptide bonds are a type of amide bond, formed between amino acids.
2. **Partial Double Bond Character**: The peptide bond has a partial double bond character due to resonance, which restricts rotation and contributes to the rigidity of protein structures.
3. **Hydrophobic Nature**: Some amino acids are hydrophobic, and their interactions contribute to the overall hydrophobic nature of protein structures.
4. **Hydrogen Bonding**: Hydrogen bonds can form between different parts of the protein backbone or between side chains, stabilizing the protein structure.
5. **Disulfide Linkages**: These are covalent bonds that can form between cysteine residues, contributing to the tertiary structure of proteins.

### Step 3: Analyze the Statements
Now, we will evaluate the given statements (A, B, C, D) regarding peptide linkages:

- **Statement A**: "It is an amide linkage."
- **Evaluation**: This statement is **correct** because peptide bonds are indeed a type of amide linkage.

- **Statement B**: "It has partial double bond character."
- **Evaluation**: This statement is **correct** as peptide bonds exhibit partial double bond character due to resonance.

- **Statement C**: "It is hydrophobic in nature."
- **Evaluation**: This statement is **correct** in the context that certain amino acids contribute to hydrophobic interactions within proteins.

- **Statement D**: "It connects protein molecules through hydrogen bonds."
- **Evaluation**: This statement is **correct** because hydrogen bonds can form between different parts of the protein, aiding in stabilization.

### Conclusion
Based on the evaluations:
- Statements B, C, and D are correct.

### Final Answer
The correct statements regarding peptide linkage in a protein molecule are B, C, and D.

---