An enzyme speeds up a chemical reaction in the cell, but can only be used once. a. true b. false

This is false.

Enzymes are actually made up by proteins which can act as a biological catalysts that can speed up chemical reactions. Each of them has an active site, its like a concaved space, and it can bind into specific substrates then combine them to form products.

However, active sites will not be changed and they can bind into more substrates again and again. Just note that the active site may only be changed due to the unfavorable temperature or pH, but otherwise they can be used again and again