Adenosine triphosphate (ATP) is created in organisms through the processes of photosynthesis, glycolysis, cellular respiration and fermentation. Photosynthesis and fermentation are restricted to plants and fungi, respectively, but glycolysis and respiration occur in both plant and animal cells.
Photosynthesis is the process by which photons are filtered through chloroplasts in plant cells. This process creates ATP and electron carriers, which are then converted into carbohydrates such as glucose.
Glycolysis occurs either when a plant consumes its stored glucose or when the plant is consumed by another organism. Two ATP are created as a result of the breakdown of glucose into two pyruvate subunits. During cellular respiration, pyruvate is then combined with oxygen, creating carbon dioxide, water and 16 ATP per unit of pyruvate.
Fermentation converts pyruvate into ATP, carbon dioxide and ethanol. While not as efficient as other methods, fermentation is able to produce ATP in an anaerobic environment.