How does an enzyme work?

Enzymes are proteins, which are made up of long chains of aminoacids. Proteins have a primary structure (the sequence of aminoacids in the chain), a secondary structure (specific 3D shapes of the chain formed through hydrogen bonds), a tertiary structure (specific 3D folding of the chain, held together via hydrogen, covalent, ionic and disulphide bonds) and a quaternary structure (specifc 3D association of multiple aminoacid chains). Enzymes are a class of functional proteins found throughout nature. Their role is to catalyse chemical reactions by lowering the activation energy of those specific reactions.

Enzymes have multiple binding sites on the surface of their 3D shape. These can be active sites, where the substrate binds in order to undergo a specific chemical reaction catalysed by the enzyme. The binding between an enzyme and its substrate can be explained by 2 different hypotheses: the ‘key and lock’ mechanism and the ‘induced fit’ mechanism. The first one means they have complementary shapes, while the second one means the enzyme undergoes conformational changes to fit the substrate. Binding sites can also be allosteric sites (‘allo-‘ meaning different and ‘-steric’ meaning location), which bind effector molecules which regulate the activity of the enzyme