The presence of oxygen, nutrients and space to discard their metabolic products are the conditions for cellular respiration in aerobic organisms. Anaerobic organisms require an absence of oxygen and the presence of different nutrients from their aerobic counterparts.
Respiration is the set of metabolic processes that the cells of a living organism completes to convert biochemical energy from nutrients into ATP. Nutrients that aerobic cells commonly use in respiration include sugar, amino acids and fatty acids.
Respiration involves catabolic reactions, where large molecules are broken down into smaller ones. The chemical bond energy of these large molecules is released in the process and utilized by the cell to do useful work. Examples of vital functions that utilize energy produced during respiration include biosynthesis, locomotion and active transport of chemical components.
To break these larger molecules into smaller ones, the cells require oxygen to oxidize these larger molecules. The predominant type of reaction in any organism’s respiratory process is the redox reaction, where some component is oxidized at the expense of the reduction of another component.
Respiration is sometimes classified as a controlled combustion reaction because the rate of release of energy from respiration in living organisms is much slower than if these reactions took place in vitro.