Metabolism can be thought of a the many reactions that occur in cells which provide the energy that is necessary to keep organisms alive. The reactions that occur in cells can be grouped into two categories; either anabolic, those reactions that take small, low energy molecules and build them into larger, higher energy molecules or catabolic reactions, those reactions that take large, high energy molecules and break them down to release energy which is captured in the molecule ATP. This ATP can then be used to provide energy to other anabolic reactions in the cell that require energy. All of these reactions in the cell are facilitated by enzymes, proteins that speed up the rate of reactions.
The next series of videos will walk you through all of the steps that can be thought of as part of the various metabolic processes that occur in living things. The processes that are covered here are only a small number of those that exist in cells, but are the ones that are at the core of the life of cells