There are two main categories of reactions in cell chemistry.
CATABOLIC reactions BREAK DOWN food molecules and release energy and chemicals for further use.
ANABOLIC reactions BUILD UP complex molecules required by the cell. Anabolic reactions depend on catabolic reactions to provide energy and materials.
METABOLISM is the working together of catabolic and anabolic reactions.
In most cases the energy needed to make cells work is provided directly or indirectly by sunlight.
Some bacteria are able to obtain energy from chemicals they encounter in their environment. These bacteria are an example of the pieces of the ‘jigsaw’ that are not seen in the ‘big picture’.
In plants light energy changed to chemical energy donates the energy needed for anabolic reactions. The chemical building blocks needed for construction come from mineral salts and water in the soil.
Inside cells energy is released from food molecules by chemical reactions. These take place in an ordered sequence beginning in the liquid cytoplasm and then in two different parts of the mitochondria. Mitochondria are organelles suspended in the cytoplasm of the cell.
All higher forms of life depend on sunlight providing energy, to drive the anabolic reaction called photosynthesis.