Photosynthesis is a vital process that occurs in plants, algae, and certain bacteria, allowing them to convert light energy into chemical energy in the form of glucose (sugar). During photosynthesis, the source of electrons is water, which is oxidized (loses electrons) to produce oxygen gas (O2).
The electrons from water are transferred to an electron acceptor molecule, which ultimately ends up being NADP+ (nicotinamide adenine dinucleotide phosphate), where it is reduced to form NADPH (nicotinamide adenine dinucleotide phosphate reduced form).
NADPH plays an important role in the next stage of photosynthesis, the light-dependent reactions, as it provides the electrons needed to power the production of ATP (adenosine triphosphate), the primary energy currency of cells.
The energy from ATP is then used to drive the light-independent reactions, where carbon dioxide (CO2) is converted into glucose through the process of carbon fixation.
Photosynthesis is the opposite of cellular respiration, which is the process by which cells produce ATP by oxidizing organic molecules like glucose.
In cellular respiration, the source of electrons is NADH (nicotinamide adenine dinucleotide reduced form) or FADH2 (flavin adenine dinucleotide reduced form), and their final destination is water, which acts as the electron acceptor. This process produces oxygen gas and generates ATP as a byproduct.
The source of electrons in photosynthesis is water, which is oxidized to produce oxygen and NADPH. In cellular respiration, NADH and FADH2 are the sources of electrons and water acts as the final destination. Understanding the role of electrons in photosynthesis and cellular respiration is crucial to understanding the overall energy balance of cells and the biosphere.