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Photosynthesis, in its broadest sense, refers to the synthesis of chemical compounds through the use of light. In the narrower sense, as used here, it refers to the process by which plants, algae, cyanobacteria, and phototrophic bacteria convert light energy to chemical form of the energy. The majority of photosynthesis is coupled to carbon assimilation in the form of carbon dioxide or bicarbonate ions, but there is also CO₂ assimilation that is not coupled to photosynthesis, as well as photosynthesis that is not coupled to carbon assimilation.
Oxygenic Photosynthesis
Oxygenic photosynthesis occurs in a variety of organisms, including eukaryotic microorganisms such as algae and bacteria such as cyanobacteria; the same mechanism is at work in both. Electron flow occurs via two distinct electron transport chains that are linked; these electron transport chains are collectively referred to as the Z scheme. Photosystem I (PSI) and photosystem II (PSII) are the stars of each chain, with chlorophyll reaction centers surrounded by antenna pigments.
For the wavelengths of light that each absorbs most efficiently, PSI chlorophyll is known as P700, and PSII chlorophyll is known as P680. The procedures are outlined below.
PSII absorbs light energy (a photon of light), which excites P680 and converts it into a good electron donor, reducing the first member of the electron transport chain, pheophytin.
PSII is normally very electropositive, and unless excited by light, it will remain reduced.
Water is split to produce electrons, which are then used to return P680 to its resting state. Water protons (H⁺) act to generate the proton motive force, while oxygen is released (giving the pathway its name).
The electrons pass through several electron carriers before reducing P700 in PSI. After absorbing light and donating an electron to the next electron transport chain, P700 has already been oxidised.
The final step in the process is the reduction of NADP⁺ to NADPH after it has passed through a series of electron carriers.
Aside from producing NADPH, electron transport generates the proton motive force, which is used by ATP synthase to produce ATP.
For the wavelengths of light that each absorbs most efficiently, PSI chlorophyll is known as P700, and PSII chlorophyll is known as P680. The procedures are outlined below.
The amazing thing about microbes is their resistance to adverse conditions. When PSII is blocked, for example, some oxygenic phototrophs can use cyclic photophosphorylation with PSI alone in the same way that oxygenic phototrophs do. Instead of oxidising water, they use H₂S or H₂ as an electron donor to supply the reducing power (the electrons) for CO₂ fixation.
Chlorophylls
Chlorophylls are a type of pigment that is made up of protoporphyrin complexed with magnesium. Chlorophylls serve as light receptors as well as special photochemical devices in photosynthetic reaction centers in photosynthetic organisms.
Ozone
Ozone is a trace constituent of the stratosphere that contributes to the formation of the ozone layer. It is made up of three oxygen atoms arranged in an open triangle. Ozone is formed in the three-body reaction O + O₂ + M= O₂ + M, where M is a stabilizing molecule (N₂ or O₂) and O is formed by photochemical dissociation O₂. Other components (NO, Cl, CFCs) catalyze the ozone destruction reaction O₃ + O = 2O₂ .The unique ability of ozone to block solar UV in a range particularly harmful to organic macromolecules (230–290 nm) makes it critical for life preservation. It also contributes to global warming.
Chloroplast
Chloroplast is a chlorophyll-containing organelle found in phototrophic eukaryotes that is responsible for energy generation from radiation. The presence of membrane-enclosed structures known as organelles, which are absent in prokaryotic cells, is a distinguishing feature of eukaryotic cells. These include mitochondria and chloroplasts, the latter of which can only be found in photosynthetic cells. Chloroplasts, like mitochondria, have a permeable outermost membrane, a much less permeable inner membrane, and an intramembranous space. The inner membrane, known as the stroma, surrounds the chloroplast lumen.
Chlorophyll and all other photosynthesis-related components are found in a series of flattened membrane discs known as thylakoids. Because its function is to establish the proton motive force required for ATP synthesis, the thylakoid membrane is highly impermeable to ions and other metabolites. Thylakoids are typically stacked into discrete structural units called grana in green algae and plants.
Cyanobacteria
Cyanobacteria are photosynthetic bacteria that use water as a reducing agent in order to produce oxygen. They appear early in Earth’s history. Cyanobacteria are privileged among organisms due to their role in the carbon and nitrogen cycles as bacterial primary producers. Because of their tolerance of a wide temperature range, desiccation, freeze-melt, and salinity stress, they are widely adapted to different extreme environments and play an important role, particularly in cold polar and alpine environments.
Electron Donor
Any organic or inorganic substance that acts as a reducing agent in an enzymatic reaction is an electron donor. In a strict sense, the reducing agent at the start of an electron transport chain or the substrate used to obtain energy through respiration.
Photosynthesis
Photosynthesis is the metabolic process by which organisms capture light and use it to perform endergonic synthesis of organic molecules. In general, photosynthesis is the primary event in the process of converting the energy associated with photons into a gradient of electrochemical potential of protons across some biological membranes, that is, into a proton motive force.
Electron Donor
Any organic or inorganic substance that acts as a reducing agent in an enzymatic reaction is an electron donor. In a strict sense, the reducing agent at the start of an electron transport chain or the substrate used to obtain energy through respiration.
Respiration
At the cellular level, respiration is the process by which biological systems oxidize various substrates, with the oxidizing agent being an external substance to the system. Historically, the term has been applied when the external electron acceptor is oxygen (aerobic respiration). This definition, however, should be broadened to include cases where the external electron acceptor is a substance other than oxygen (anaerobic respiration).
Electrophoresis
The migration of charge molecules (for example, nucleic acids or proteins) through a medium according to charge and molecular size as a result of an applied electric current and interactions with the medium is known as electrophoresis. Matrix composition and concentration, ionic strength, electrical current strength and field angle, and migration time are all variables that can be changed. Capillary electrophoresis (CE), gel electrophoresis (GE), and pulsed-field gel electrophoresis (PFGE) are commonly used for chromosomal DNA separation; denaturing and/or temperature gradient gel electrophoresis (DGGE/TGGE) for sequence separation; polyacrylamide gel electrophoresis (PAGE) and SDS-PAGE for protein separation in their native and denatured conformations, respectively; and isoelectric focusing .
Conclusion
Photosynthesis, in its broadest sense, refers to the synthesis of chemical compounds through the use of light. In the narrower sense, as used here, it refers to the process by which plants, algae, cyanobacteria, and phototrophic bacteria convert light energy to chemical form of the energy. Oxygenic photosynthesis occurs in a variety of organisms, including eukaryotic microorganisms such as algae and bacteria such as cyanobacteria; the same mechanism is at work in both. Chlorophylls are a type of pigment that is made up of protoporphyrin complexed with magnesium. Chlorophylls serve as light receptors as well as special photochemical devices in photosynthetic reaction centers in photosynthetic organisms. Ozone is a trace constituent of the stratosphere that contributes to the formation of the ozone layer. It is made up of three oxygen atoms arranged in an open triangle. Chloroplast is a chlorophyll-containing organelle found in phototrophic eukaryotes that is responsible for energy generation from radiation. Any organic or inorganic substance that acts as a reducing agent in an enzymatic reaction is an electron donor. Photosynthesis is the metabolic process by which organisms capture light and use it to perform endergonic synthesis of organic molecules. At the cellular level, respiration is the process by which biological systems oxidize various substrates, with the oxidising agent being an external substance to the system.
