Paper 1 Q9 — How enzymes lower activation energy

What the examiners said

“Option B… that enzymes reduce the activation energy by breaking bonds, was the most commonly selected… the relationship is the opposite way round — a reduction in activation energy means that less energy is required to break bonds. [Others] had confused the complementary base pairing of nucleic acids with the complementary fit between substrate and active site.”

Explore — lower the barrier, not the bonds

Add an enzyme to lower the activation-energy barrier and watch the fraction of molecules able to get over it rise — without the enzyme supplying any energy itself.

Note the reactant and product energy levels are unchanged — only the barrier height falls. Enzymes change the path, not the energetics of reactants and products.