A peptide chain attains secondary structure through the formation of

Options

A. Peptide bonds
B. Intrachain ionic bonds
C. Intrachain hydrogen bonds
D. Intrachain disulphide bonds.

Answer

To answer the question "A peptide chain attains secondary structure through the formation of?", we will analyze the options provided and identify the correct one step by step.

### Step 1: Understand the Structure of Proteins
Proteins are made up of amino acids linked together by peptide bonds. The sequence of these amino acids constitutes the primary structure of the protein.

**Hint:** Remember that the primary structure is just the sequence of amino acids linked by peptide bonds.

### Step 2: Define Secondary Structure
The secondary structure of a protein refers to the local folded structures that form within a polypeptide due to interactions between the backbone atoms in the amino acid sequence. This includes structures such as alpha helices and beta sheets.

**Hint:** Secondary structure involves the folding or coiling of the polypeptide chain.

### Step 3: Identify Stabilizing Interactions
The secondary structure is stabilized primarily by hydrogen bonds that form between the backbone atoms of the polypeptide chain. These hydrogen bonds occur between the carbonyl oxygen of one amino acid and the amide hydrogen of another.

**Hint:** Look for interactions that stabilize the folded structures in proteins.

### Step 4: Analyze the Options
- **Peptide bond:** This is incorrect as it relates to the primary structure.
- **Intrachain ionic bond:** While ionic bonds can play a role in tertiary structure, they are not the primary stabilizing force in secondary structure.
- **Intrachain hydrogen bond:** This is correct as it directly relates to the stabilization of secondary structures like alpha helices and beta sheets.
- **Intrachain disulfide bonds:** These are covalent bonds that help stabilize tertiary structure, not secondary.

### Conclusion
The correct answer is **intrachain hydrogen bonds**. These bonds are responsible for the formation of the secondary structure in peptide chains.

**Final Answer:** Intrachain hydrogen bonds.