Numbers of variable regions on each light and heavy chain of an antibody –
Correct Answer: 1
Description: Ans. is 'a' i.e., 1 Immunoglobulin o Immunoglobulins are molecles that are produced by plasma cells in response to an immunogeno Immunoglobulins are glycoproteins o Each immunoglobulin is composed of two light chains (L) and two heavy chains H.o The L chain has a molecular weight of25000, and the H cain of 50000o The L chain is attached to H. chain by disulphide band.o the two H cains are joined together by disulphide bonds.o Immunoglobulin isotype (ie C, M, A, D, E,) is determined by the type of Ig heavy chin present:Immunoglobulin classH. chainIgGg(gamma)IgAa(alpha)IgM(mu)Ig Dd (delta)IgEE (epsilon)o The L chains are similar in ail classes of immunoglobulins either kappa or lambda (kappa being more common).o Antigen combining site is at amino-terminus and is composed by both L and H chains,o Both H and L chains consist of two units; constant and variable:H chain-One variable (VH) and three or four constant units (CH)L chain-One variable (VL) and one constant (C2) unit,o The variable region is further subdivided into hypervariable region and frame work region.o Hypervariable regions at aminoterminal are involved in formation of antigen binding sites,o L chain has three hypervariable regions and H chain has four. Hypervariable regions are also called as 'Hot spots o Sites on the hypervariable regions which make actual contact with the epitopes are called complementarity determining regions (CDRs).o The infinite range of the antibody specificity of immunoglobulins depends on the variability of the aminoacid sequences at the variable units of H and L chains.o Fc fragment is composed of the carboxvterminal. It determines the biological activity such as complement fixation, placental transfer, skin fixation and catabolic rate.o CH-2, of Ig G and CH4 of IgM bind to C1q portion of C1
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Microbiology
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