Two polypeptide chains are joined by hydrogen bonds to produce

Options

A. `alpha`-helix
B. Tertiary structure
C. `beta`-pleated sheet
D. All the above.

Answer

To solve the question "Two polypeptide chains are joined by hydrogen bonds to produce," we can follow these steps:

### Step 1: Understand the Components
- **Polypeptide Chains**: These are long chains of amino acids linked by peptide bonds. Proteins are made up of one or more polypeptide chains.
- **Hydrogen Bonds**: These are weak bonds that can form between certain polar molecules, including between the amino acids in polypeptide chains.

### Step 2: Identify the Structures
- **Alpha Helix**: A common secondary structure in proteins where the polypeptide chain coils into a helical shape, stabilized by hydrogen bonds.
- **Beta Pleated Sheet**: Another type of secondary structure where two or more polypeptide chains lie alongside each other and are held together by hydrogen bonds.
- **Tertiary Structure**: The overall three-dimensional shape of a single polypeptide chain, which is stabilized by various interactions, including hydrogen bonds, but not specifically formed by the joining of two polypeptide chains.

### Step 3: Analyze the Question
The question specifically mentions "two polypeptide chains" joined by hydrogen bonds. This indicates that we are looking for a structure that is formed by the interaction of two separate polypeptide chains.

### Step 4: Determine the Correct Answer
- The beta pleated sheet is formed when two or more polypeptide chains are aligned and stabilized by hydrogen bonds. Therefore, the correct answer to the question is **beta pleated structure**.

### Conclusion
The correct answer to the question is **beta pleated structure**.

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