Given a scientific passage and an answer, generate a question for the given answer.

Passage: Plants and animals exist in a cycle; each requires products of the other. The thousands of coordinated chemical reactions that keep cells alive are referred to collectively as metabolism. In general, metabolic reactions are divided into two classes: the breaking down of molecules to obtain energy is catabolism, and the building of new molecules needed by living systems is anabolism. Answer: anabolism
What is the term for the metabolic reaction where living systems build new molecules?