If one or more of the amino acids incorporated into the variable regions of this antibody were changed, which of the following would most likely also be true? the constant region would also change. the amino acid sequence of the associated antigen would also change. the antibody would no longer bind the same antigens. the antibody would bind a broader range of antigens.

From a chemical point of view, proteins are by far the most structurally  complex  and functionally sophisticated molecules known. this is perhaps not surprising, once one realizes that the structure and chemistry of each  proteinhas been developed and fine-tuned over billions of years of evolutionary history. we start this chapter by considering how the location of each  amino acid  in the long string of amino acids that forms a protein determines its three-dimensional shape. we will then use this understanding of protein structure at the atomic level to describe how the precise shape of each protein  molecule  determines its function in a cell.