Question

Enzymes work to speed up chemical reactions in the body. What do enzymes actually do to speed up reactions? Are the reactants and products changed by the enzymes?

Answer 1

Enzymes act as a catalyst they speed up reactions by providing a alternative pathway of lower activation energy by attaching to itself to its specific substrate and breaking down the energy required to start the process making it quicker. 
And no they just speed the process up :)