Which of the following statements concerning the chemical structure of an antibody is false?

• A. Antibodies contain disulfide bonds that help stabilize their structure.
• B. Antibodies are composed of four polypeptide chains: two heavy chains and two light chains.
• C. Antibodies are made entirely of carbohydrate molecules.
• D. The variable region of an antibody is responsible for antigen binding.

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the basic structure of antibodies. Antibodies are proteins composed of four polypeptide chains: two heavy chains and two light chains, connected by disulfide bonds.
2. Step 2: Recognize the role of disulfide bonds. These covalent bonds stabilize the three-dimensional structure of the antibody by linking the polypeptide chains together.
3. Step 3: Identify the function of the variable region. The variable region of an antibody is the part that binds specifically to an antigen, allowing the immune system to recognize and target foreign molecules.
4. Step 4: Evaluate the statement about carbohydrate composition. While antibodies can have carbohydrate groups attached (glycosylation), they are not made entirely of carbohydrate molecules; their main structure is protein-based.
5. Step 5: Conclude that the false statement is the one claiming antibodies are made entirely of carbohydrate molecules, as this contradicts the fundamental protein nature of antibodies.