Topic summary
Metabolic wastes
Extracted from the Wikipedia article Metabolic waste.
Metabolic wastes or excrements are substances left over from metabolic processes (such as cellular respiration) which cannot be used by the organism (they are surplus or toxic), and must therefore be excreted. This includes nitrogen compounds, water, CO2, phosphates, sulphates, etc. Animals treat these compounds as excretes. Plants have metabolic pathways which transform some of them (primarily the oxygen compounds) into useful substances, while others are stored, released into the environment, or broken down through further biochemical processes.