This chapter considers oxygenic photosynthesis as the most important biochemical process on earth. With a few minor exceptions, photosynthesis is the only mechanism by which an external abiotic source of energy is harnessed by the living world, and it is the source of O2, which sustains all aerobic organisms. It explains photosynthesis as the light-driven biochemical mechanism whereby CO2 is incorporated into organic molecules, such as glucose. The chapter refers to captured light energy that is used to synthesise adenosine triphosphate (ATP) and nicotinamide adenine dinucleotide phosphate (NADPH), which drive the process. The reducing power of NADPH is necessary as a strong electron donor is required to reduce the fully oxidised, low-energy carbon atoms in CO2 to the carbon units of organic molecules.
Chapter
Photosynthesis
Chapter
Eukaryotic photosynthesis
This chapter argues that oxygenic photosynthesis is the most important form of photosynthesis on Earth, which accounts for an estimated 3000-fold greater amount of carbon fixation. It discusses the emerging evidence that oxygenic photosynthesis might have its origins close to the beginnings of cellular life at around or before 4 Ga. It also recognizes oxygenic photosynthesis as the only form that was acquired by eukaryotes following a unique endosymbiotic event between a eukaryotic heterotroph and a cyanobacterium. The chapter focuses on the mechanisms of oxygenic photosynthesis in eukaryotes, and cites algae and plants. It also presents a comparative analysis of the extant cyanobacterial mechanisms which had a momentous effect on biological evolution.
