Site Loader

First, I’ll start off with some differences between oxygenic photosynthesis and anoxygenic photosynthesis. According to PEDIAA.com, algae, plants and cyanobacteria photosynthesize by oxygenic photosynthesis. Oxygenic photosynthesis final electron acceptor is water. Anoxygenic photosynthesis is used by some bacteria. Anoxygenic photosynthesis does not produce any oxygen. Nonsulf bacteria, green sulfur bacteria, heliobacteria, purple bacteria, and acidobacteria photosynthesize by anoxygenic photosynthesis. In oxygenic photosynthesis, photosystems I and II are used, whereas only photosystem I is used in anoxygenic photosynthesis. Oxygenic photosynthesis uses water has the electron source and hydrogen, hydrogen sulfide or ferrous ions are used as the electron donor in anoxygenic photosynthesis. If not obvious enough in oxygenic photosynthesis, oxygen is produced during the light reaction. In anoxygenic photosynthesis, oxygen is not being produced during the light reaction like in oxygenic. In oxygenic photosynthesis, chlorophylls are used and in anoxygenic photosynthesis, bacteriochlorophylls or chlorophylls are used. NADPH is produced in oxygenic photosynthesis because ADP is the terminal electron acceptor. Anoxygenic photosynthesis doesn’t produce NADPH like oxygenic does because the electrons are reentered into the system. In oxygenic photosynthesis, ATP is produced by noncyclic photophosphorylation whereas cyclic photophosphorylation produces ATP in anoxygenic photosynthesis. Oxygenic photosynthesis equation is shown as 6CO2 + 6H2O ?Light C6H12O6 + 6O2. Anoxygenic photosynthesis is shown as 6CO2 + 12H2S + Light ? C6H12O6 + 12S + 6H2O. (PEDIAA, 2018)
According to our text book, in light reactions in cyanobacteria and photosynthetic eukaryotic cells, photosystem I and photosystem II work together as part of the light reactions. The energy that is absorbed by photosystem I and photosystem II raise the energy of electrons stripped from water to a high enough level that it can be used to generate a proton motive force and produce reducing power. This is why it is considered oxygenic photosynthesis because it does just that, it generates oxygen. (Anderson, D. G., et al., 2016) According to News.net, “All living and breathing organisms inhale oxygen from the air to produce energy and exhale carbon dioxide into the atmosphere. Oxygenic photosynthesis replaces oxygen in the air with the assistance of energy from sunlight.” In our text book, the Tandem Photosystems of Cyanobacteria and Chloroplasts, energy that is captured by antennae pigments excites a reaction center chlorophyll. This causes it to emit a high energy electron, which is passed to an electron transport chain. In cyclic photophosphorylation, electrons emitted by photosystem I are returned to that photosystem. In non-cyclic photophosphorylation, the electrons used to replenish photosystems I are donated by radiant energy, excited photosystem II. Then, photosystem II replenishes its own electrons by stripping them from water, in return, producing oxygen. (Anderson, D. G., et al., 2016) On News.net, I found if there wasn’t oxygenic photosynthesis, eventually our atmospheric oxygen would be completely gone. After an oxygenic photosynthesis reaction, six carbon dioxide molecules come together with twelve molecules of water with the use of sunlight. The sunlight is required for this reaction to occur. Oxygenic photosynthesis reacts to form six oxygen molecules, one glucose molecule and six water molecules. (News, 2017)
According to Anderson, D. G. et al., anoxygenic photosynthetic bacteria have only a single photosystem. It cannot use water as an electron donor for reducing power. This is exactly why it is considered anoxygenic, it does not generate oxygen. Hydrogen gas, hydrogen sulfide, and organic compounds is what anoxygenic photosynthetic bacteria use as electron donors. (Anderson, D. G., et al., 2016) The way anoxygenic photosynthesis uses light energy resembles how plants use light energy as well. Anoxygenic photosynthesizing bacteria and plants are photoautotrophs because they use carbon dioxide to create energy. But aside from having that in common they do differ from how anoxygenic photosynthesis only uses the use of photosystem I for collecting energy from the sunlight and plants use both photosystems.(Study) According to our text book, there are two groups of anoxygenic photosynthetic bacteria, purple bacteria and green bacteria. The purple bacteria will use a photosystem that resembles photosystem II in oxygenic photosynthesis of cyanobacteria and eukaryotes to use ATP. They have to use the reverse electron transport because the photosystem odes increase the electrons to a high enough standard level to decrease NAD+. The reverse electron transport is what it sounds, it’s the electron transport chain ran in reverse by the use of ATP. Green bacteria use a photosystem close in relation to the photosystem I in oxygenic photosynthesis of cyanobacteria and eukaryotes. A reduction of NAD+ or generation of a proton motive force is caused from the electrons being released. (Anderson, D. G., et al., 2016)

Post Author: admin