Final answer:
A particle that binds in the active site of an enzyme to prevent substrate binding is called a competitive inhibitor. These inhibitors resemble the substrate and directly compete with it for active site binding, unlike non-competitive inhibitors that bind to allosteric sites.
Step-by-step explanation:
A particle that can bind in the active site of an enzyme, preventing the binding of the substrate, is referred to as a competitive inhibitor. Competitive inhibitors are molecules that compete with the substrate for the active site of an enzyme. Unlike non-competitive inhibitors, which bind to an allosteric site causing conformational changes to the enzyme that reduce its effectiveness, competitive inhibitors directly block the substrate from binding by occupying the active site themselves. This is highlighted by the fact that a competitive inhibitor most structurally resembles the substrate it competes with.