Photosynthesis

In the prototypical form of the biological process of photosynthesis in green plants, the leaves capture energy from the photons in sunlight and use that captured energy as the essential primary energy source to drive a set of biochemical reactions that converts carbon dioxide (CO₂) and water (H₂) to oxygen (O₂) and a carbohydrate compound, the sugar, glucose (C₆H₁₂). The process effectively stores energy in the sugar molecule that the photosynthetic cell can metabolize to generate adenosine triphosphate (ATP), the universal energy currency of the cell, so-called because it can provide the energy needed to drive biochemical reactions necessary to synthesize the nutrients required to maintain the cell in a living state. Photosynthesizing cells thus convert light energy to life-sustaining chemical energy.

Organisms that photosynthesize, functioning as autotrophs — organisms that generate their own source of food-energy — with their photon-energy-derived complement of carbohydrates, proteins and lipids, directly provide a source of food-energy (e.g., vegetables, fruits) for consumption by us humans and other organisms, so-called heterotrophs, and indirectly provide a source of food-energy in the form of the non-human heterotrophs that we consume (chickens, fish). Photosynthesizing cells also supply the oxygen we need to generate our own ATP, and they consume the 'waste' CO₂ produced in the process of generating ATP.

This article will classify the differing types of photosynthesizing organisms, and describe the details of the differing photosynthetic mechanisms employed by them. It will also discuss the implications of photosynthesis in the sciences of biology, geology, oceanography, climatology, and other areas of importance to the life of planet Earth.

Preliminarily, the reader might refer to the following: