(N/A) $\Rightarrow$ Each enzyme $(E)$ has a substrate $(S)$ binding site in its molecule where the substrate binds to form an enzyme-substrate complex $(ES)$. It soon dissociates into its product $(P)$ and the unchanged enzyme,with an intermediate formation of an enzyme-product complex $(EP)$.
$\Rightarrow$ The formation of the $ES$ complex is essential for catalysis.
$\Rightarrow$ The reaction sequence is: $E + S \rightleftharpoons ES \longrightarrow EP \longrightarrow E + P$
$\Rightarrow$ It can be explained in the following steps:
$(1)$ First,the substrate binds to the active site of the enzyme,fitting into the active site.
$(2)$ The binding of the substrate induces the enzyme to alter its shape,fitting more tightly around the substrate.
$(3)$ The active site of the enzyme,now in close proximity to the substrate,breaks the chemical bonds of the substrate,and a new enzyme-product complex $(EP)$ is formed.
$(4)$ The enzyme releases the products of the reaction,and the free enzyme is ready to bind to another molecule of the substrate to run through the catalytic cycle once again.