Question

which statement best explains how enzymes speed up chemical reactions?
o enzymes lower the activation energy of a reaction.
o enzymes increase the distance between reactant molecules.
o enzymes provide heat to chemical reactions.
o enzymes increase the concentration of the reactants.

Explanation:

Enzymes act as catalysts. They lower the activation - energy barrier that reactant molecules must overcome to form products, thus speeding up the reaction. Increasing distance between reactant molecules would slow down reactions, enzymes don't provide heat, and they don't increase reactant concentration.

Answer:

Enzymes lower the activation energy of a reaction.