The small energy input every chemical reaction needs to get started is the:

1. Even a reaction that releases energy overall does not start on its own contact. 2. The reacting molecules must first be pushed into a strained arrangement. 3. This small amount of energy input necessary for all chemical reactions to occur is called the activation energy. 4. It is abbreviated EA and is always positive. _Source: OpenStax Biology for AP(R) Courses (CC BY 4.0), Ch 6 'Metabolism', sections 6.1-6.5_