An antibody molecule consists of
Correct answer: C. four polypeptide chains, two heavy and two light, arranged in a Y shape
- A. a single polypeptide chain
- B. two identical polypeptide chains
- C. four polypeptide chains, two heavy and two light, arranged in a Y shape
- D. a chain of nucleotides folded into a Y shape
Explanation
The two arms of the Y carry the variable regions that give each antibody its specific antigen binding sites, while the constant stem determines the class and how the antibody is disposed of. Antibodies are immunoglobulins, that is proteins, so a nucleotide structure is impossible. The two binding sites are what allow an antibody to clump antigens together in agglutination.
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About Specific Defense Mechanism
Specific defense mechanisms provide targeted immunity through B lymphocytes, T lymphocytes, antibodies and memory cells that recognize particular antigens. Questions cover humoral and cell mediated responses, clonal selection, primary and secondary immune responses, vaccination and passive immunity, while distinguishing adaptive defenses from the immediate, non specific innate response.
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