Which antibody has five antibody molecules connected to form a starburst shape?

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Multiple Choice

Which antibody has five antibody molecules connected to form a starburst shape?

Antibody structure varies by class, and one form stands out as a pentamer: five antibody units joined together. This creates a starburst (flower-like) shape because the five Y-shaped monomers are linked by a joining chain and disulfide bonds around a central hub. This pentameric arrangement gives IgM ten antigen-binding sites (two per monomer), boosting its ability to cross-link antigens and strongly activate the classical complement pathway via C1q. Other antibody classes are not pentamers: IgG is a single monomer, IgA is typically a dimer in secretions (two monomers linked by a joining chain), and IgE is also a monomer. So the starburst pentamer corresponds to IgM.

Antibody structure varies by class, and one form stands out as a pentamer: five antibody units joined together. This creates a starburst (flower-like) shape because the five Y-shaped monomers are linked by a joining chain and disulfide bonds around a central hub. This pentameric arrangement gives IgM ten antigen-binding sites (two per monomer), boosting its ability to cross-link antigens and strongly activate the classical complement pathway via C1q.

Other antibody classes are not pentamers: IgG is a single monomer, IgA is typically a dimer in secretions (two monomers linked by a joining chain), and IgE is also a monomer. So the starburst pentamer corresponds to IgM.

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