An antibody is built from _________ polypeptide chains?
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Answer: D. 4
Explanation
Standard antibodies consist of four interconnected polypeptide protein chains. Two identical heavy chains form the core structural backbone. Two identical light chains attach via disulfide bonds to complete the molecule. Immunoglobulins are Y-shaped proteins produced by plasma B cells. Disulfide covalent bonds hold the four polypeptide chains securely together. Variable regions at the tips bind specifically to matching foreign antigens.
The adaptive immune system relies on diverse antibodies to neutralize pathogens. Monoclonal antibodies are engineered tools used in modern medical therapies. Serological testing detects specific antibodies to diagnose infectious diseases. One polypeptide chain is insufficient to form a functional antibody structure. Two polypeptide chains describe simpler receptor proteins or half-molecules. Three polypeptide chains lack the symmetrical structure of immunoglobulins.
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