sentence2_structure: organisms<>use<>catalysis<>to speed up reactions$$$organisms<>use catalysis to speed up<>reactions
sentence1: CATALYSIS The defining property of all catalysts is that they increase the speed of a chemical reaction without being used up or appearing as one of the products of the reaction.
sentence2: Instead of heat, organisms use catalysis to speed up reactions.
question: Instead of heat, organisms use what to speed up reactions?