Question

The two heavy chains of a human antibody are linked to each other by:

• A. Hydrogen bond
• B. Glycosidic bond
• C. Phosphodiester bond
• D. Disulfide bond

Hint:

Disulfide bonds are essential for the structural stability of antibodies and many other proteins. These covalent bonds help proteins maintain their active conformation, which is necessary for their function.

Answer 1

The Correct Option is D

Step 1: Understanding the structure of an antibody

Antibodies, also known as immunoglobulins, are made up of four polypeptide chains: two heavy chains and two light chains. The heavy chains are linked together and with the light chains by disulfide bonds, which are covalent bonds formed between the sulfur atoms of cysteine residues.

Step 2: Role of disulfide bonds

Disulfide bonds are important in stabilizing the three-dimensional structure of proteins. They form between the thiol groups of cysteine residues, linking two parts of a polypeptide chain or two different chains. In antibodies, disulfide bonds help in maintaining the quaternary structure by holding the heavy chains and light chains together.

Step 3: Explanation of other bond types

Hydrogen bonds are weak bonds that form between an electronegative atom (such as oxygen or nitrogen) and a hydrogen atom attached to another electronegative atom. While hydrogen bonds play a role in protein folding, they do not link the heavy chains of an antibody.

Glycosidic bonds are the type of bond found between carbohydrate molecules. These bonds are not involved in linking the heavy chains of antibodies.

Phosphodiester bonds are the bonds that link nucleotides in a nucleic acid strand, such as DNA or RNA. They are not relevant to the structure of antibodies.

Step 4: Conclusion

The correct bond that links the two heavy chains of a human antibody is the disulfide bond. This bond is critical for maintaining the structural integrity of the antibody and its function in immune responses.