Reactions that build complex molecules and require an input of energy are called:

1. Metabolism is composed of building and degradation. 2. The building half needs energy put in because the product stores more of it. 3. Other metabolic reactions require energy to build complex molecules, which is anabolism. 4. Catabolism runs the other way and releases energy instead. _Source: OpenStax Biology for AP(R) Courses (CC BY 4.0), Ch 6 'Metabolism', sections 6.1-6.5_