Photosynthesis in Algae
Back to 1893, Charles Barnes introduced the word ‘photosynthesis' as the biological mechanism that involves “synthesis of complex carbon compounds out of carbonic acid, in the presence of chlorophyll, under the influence of light” (Gest et al., 2002).
Algae, like plants, have the ability to transform photosynthetic active radiation energy into biologically useful energy (Pfeiffer, Ivna, et al., 2017). All organisms capable of oxygenic photosynthesis have a relatively conserved and tightly regulated biosynthetic pathway to produce these important light harvesting and energy transducing molecules, and chlorophylls and their derivatives are essential components of the photosynthetic apparatus (Cahoon & Timko, 2003).
The mechanism of oxygenic photosynthesis can be separated into light and dark phases in algae as in higher plants (Vecchi et al., 2020). During the light photosynthetic reaction, the light is captured to provide reducing power in the form of nicotinamide–adenine dinucleotide phosphate (NADPH) and metabolic energy in the form of adenosine triphosphate (ATP); whereas during the dark reactions, NADPH and ATP are then used to synthesize carbohydrates (St. Onge, 2018).
In the biochemical reaction that takes place in the chloroplast, algae use the chlorophyll to absorb light, split the water molecule, and release oxygen gas, as well as the energy storage compounds NADPH and ATP, during in a light-dependent photosynthesis process (Petsas & Vagi, 2017).
Figure 1.
Algal photosynthesis process
Several algal biochemical parameters related to photosynthesis processes, such as ATP formation, CO2 fixation, O2 evolution, carbon absorption and chlorophyll quality, have been adopted as standard and classical markers for the assessment of environmental stress induced by several groups of different pollutants in photosynthetic algal species (Petsas & Vagi, 2017).