Cells have a large number of biochemical cycles which mediate life's functions. The most fundamental of these are: photosynthesis, which traps light from the sun; glycolysis, which produces energy from sugar produced with sunlight; and the Krebs cycle, which increases the rate of energy (ATP) production dramatically. The study of these reactions shows how structure and function are related to one another in cells and emphasizes that biochemical process are logical, stepwise progressions.