For most organisms metabolism requires food and what?

Metabolism is the sum of all chemical reactions that occur within a living organism. These reactions can be classified into two types: catabolism and anabolism. Catabolism is the breakdown of complex molecules into simpler ones, releasing energy in the process. Anabolism is the synthesis of complex molecules from simpler ones, requiring energy in the process.

In order to carry out these reactions, organisms need both food and oxygen. Food provides the raw materials for anabolism, while oxygen is used in catabolism to release energy. Without both food and oxygen, most organisms cannot survive.