There are literally thousands of enzymes at work in complex living systems such as human beings. What properties of enzymes give rise to their ability to distinguish one substrate from another?

Enzymes are proteins that act as biological catalysts, speeding up the rate of biochemical reactions. They have remarkable substrate specificity, meaning that they can differentiate and interact with a particular substrate among thousands of different molecules. This specificity is essential for the proper functioning of living systems. There are two main properties of enzymes that contribute to their substrate specificity: the active site's structure and its chemical properties.

The active site is the region of an enzyme where a substrate binds and undergoes a chemical reaction. The structure of the active site is crucial for substrate recognition since its shape is complementary to that of the substrate. This means that the enzyme's active site can bind to its specific substrate just like a key fits into a lock, ensuring that only the correct substrate interacts with the enzyme. In order for enzymes to distinguish one substrate from another, they rely on the carefully arranged amino acid residues within their active sites. These residues form a unique three-dimensional structure and present surfaces that are complementary to the shape and charge distribution of their specific substrates. The specificity of an enzyme can be so high that it may only recognize and bind to a single molecular configuration among thousands of closely related molecules.

The chemical properties of the active site also contribute to the enzyme's ability to recognize specific substrates. Within the active site, amino acid residues (known as the catalytic groups) are involved in forming chemical bonds with the substrate. These residues can have unique chemical properties, such as acidic, basic, hydrophilic, or hydrophobic properties, which allow them to interact with substrates through various types of interactions such as hydrogen bonds, ionic bonds, and hydrophobic interactions. These chemical interactions are vital for substrate binding and recognition, and they also play a crucial role in the enzyme-catalyzed reaction itself, helping to lower the activation energy and accelerate the reaction rate. In summary, enzymes can distinguish one substrate from another through the specific structural and chemical properties of their active sites. The complementary shape and charge distribution between the active site and its substrate, as well as the unique chemical interactions, enable enzymes to show high substrate specificity, ensuring the proper functioning of biochemical reactions in complex living systems such as humans.