Chapter 4: Natural Photosynthesis System

Sunlight, water, and carbon dioxide are the main ingredients leading to virtually all the motion and activity we see in the world. The fixation of carbon from CO₂ yields organic products in photosynthesis through two sets of reactions: light-dependent reactions and light-independent reactions. In the light-dependent reactions, harvested energy from photons excites electrons, which are transferred by redox reactions to reduce NADP⁺ to NADPH with the addition of a proton. A gradient of protons from oxidized water and those pumped by means of the excited electrons powers the generation of ATP. The light-independent reactions utilize these molecules, ATP and NADPH, to synthesize more complex molecules for long-term energy storage. This chapter outlines both sets of reactions. It describes the machinery of photosynthesis and how the components contribute in a sophisticated orchestration. Relevant cell biology is also discussed, as well as variations of the process used by plants in hot and dry environments. The potential for biomass to contribute towards meeting humanity's growing need for sources of energy is described, and a context is provided to frame efforts in mimicking natural photosynthesis to generate energy.