AP BIOLOGY

Detailed explanation-1: -The variable region of each heavy chain is approximately 110 amino acids long and is composed of a single Ig domain. Heavy chain with one variable (VH) domain followed by a constant domain (CH1), a hinge region, and two more constant (CH2 and CH3) domains.

Detailed explanation-2: -The amino acid sequences of many immunoglobulin heavy and light chains have been determined and reveal two important features of antibody molecules. First, each chain consists of a series of similar, although not identical, sequences, each about 110 amino acids long.

Detailed explanation-3: -The immunoglobulin domain: the basic IgSF building block Each V or C domain consists of approximately 110–130 amino acids, averaging 12, 000–13, 000 kDa.

Detailed explanation-4: -For example, in humans, functioning IgM antibodies have five Y-shaped units (pentamer) containing a total of ten light chains, ten heavy chains, and ten antigen-binding.

Detailed explanation-5: -An intact IgG antibody consists of two heavy chains and two light chains. Each heavy chain contains four Ig domains, one “variable” domain, and three “constant” domains; whereas each light chain contains two Ig domains, one constant and one variable.