A (n) _reaction is one that builds large molecules (polymers) from smaller molecules.

This type of reaction requires energy.

Anabolic reactions

Explanation:

Anabolic reactions -

It refers to the type of reaction, where energy in the form of heat or light is required for the reaction to take place, in this type of reaction larger molecules can be formed from smaller reactants, is referred to as anabolic reactions.

These type of reaction takes place along with catabolic reactions, that are responsible to convert the chemical energy into cellular energy, that are needed to start up an anabolic reaction.

Hence, from the given statement of the question,

The correct answer is anabolic reaction.