Metabolism refers to all of the chemical reactions that take place inside living cells. Unicellular and multicellular organisms must control their metabolism in order to survive.
Another way a metabolic pathway can be controlled is by feedback inhibition. This is when the end product in a metabolic pathway binds to an enzyme at the start of the pathway.
This process stops the metabolic pathway and so prevents further synthesis of the end product until the end product concentration decreases. The higher the concentration of end product, the quicker the metabolic pathway stops.