Protein X is able to bind all three ligands, which have similar chemical structures. Protein Y, because of the shape of its binding site, can bind only ligand c. Protein Y, therefore, has a greater chemical specificity than protein X.
Although some binding sites have a chemical specificity that allows them to bind only one type of ligand, others are less specific and thus are able to bind a number of related ligands. For example, three different ligands can combine with the binding site of protein X in Figure 4-3 since a portion of each ligand is complementary to the shape of the binding site. In contrast, protein Y has a greater—that is, more limited— chemical specificity and can bind only one of the three ligands.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.