An irreversible inhibitor is a type of molecule that permanently binds to an enzyme, blocking its activity. Unlike reversible inhibitors, which can detach from the enzyme, irreversible inhibitors form strong covalent bonds, leading to a lasting effect on the enzyme's function. This can significantly alter biochemical pathways in organisms. These inhibitors are often used in drug design to target specific enzymes involved in diseases. For example, some cancer treatments utilize irreversible inhibitors to inhibit the activity of enzymes like proteases or kinases, which play crucial roles in cell growth and division.