Photosynthesis chemical reactions

Photoperiod - the effect light has on a plant to make it bloom or not bloom Photosynthesis - chemical reaction within a plant between light and the plan. 

Chloroplasts are the site of photosynthesis, the reactions by which light energy is converted to metabolically useful chemical energy in the form of ATP. These reactions occur on the thylakoid membranes. The formation of carbohydrate from CO9 takes place in the stroma. Oxygen is evolved during photosynthesis. Chloroplasts are the primary source of energy in the light. 

As one other familiar reference, consider photosynthesis. You have undoubtedly heard many times that this is the chemical process by which a plant stores the energy of the sun. Much is known about the chemical reactions of photosynthesis and it is indeed true that they result in formation of chemical compounds with higher heat content than the starting substances. These reactions will not occur in the absence of light— the light supplies the energy required to raise the reactants to the higher heat content of the products. 

Redox reactions constitute the third of the three major classes of chemical reactions treated here. The variety of these reactions is remarkable. Many common reactions, such as combustion, corrosion, photosynthesis, the metabolism of food, and the extraction of metals from their ores, appear to be completely different. However, when we consider these changes at the molecular level with a chemist s eye, we can see that they are all examples of a single type of process. 

Why Do We Need to Know This Material The topics described in this chapter may one day unlock a virtually inexhaustible supply of clean energy supplied daily by the Sun. The key is electrochemistry, the study of the interaction of electricity and chemical reactions. The transfer of electrons from one species to another is one of the fundamental processes underlying life, photosynthesis, fuel cells, and the refining of metals. An understanding of how electrons are transferred helps us to design ways to use chemical reactions to generate electricity and to use electricity to bring about chemical reactions. Electrochemical measurements also allow us to determine the values of thermodynamic quantities. 

Photoautotrophic organisms, such as algae, cyanobacteria, and plants, all contain chlorophyll a and obtain energy by a process known as oxygenic photosynthesis. The overall chemical reaction of this process is ... 

Electron transfer reactions constitute an ubiquitous class of chemical reactions. This is particularly true in biological systems where these reactions often occur at interfaces, in photosynthesis for instance. It is therefore challenging to use the surface specificity and the time resolution of the SHG technique to investigate these processes. At liquid-liquid interfaces, these processes are mimicked through the following scheme ... 

The reaction of photosynthesis is clearly the most important chemical reaction since life could not exist for long without it. The overall reaction is... 

Combustion. An exothermic chemical reaction involving oxidation of an organic compound and results in the creation of H2O and CO2. The heat results from rupture of the chemical bonds. In the case of organic materials such as wood, the original energy was stored by photosynthesis. 

Several metabolic pathways are described in later chapters. Basically, these are seqnences of chemical reactions leading from some molecnlar starting point to some distinct end point. Photosynthesis and respiration provide two examples. 

Recently it has been reported (3 ) that in a triad molecule where a porphyrin is juxtaposed between a carotenoid and a quinone, a charge transfer donor-acceptor pair with a lifetime similar to that found experimentally in biological systems was produced on light irradiation. It was suggested that an electrical potential similar to the type developed in this donor-acceptor pair may be important in driving the chemical reactions in natural photosynthesis. 

Many of the simplest chemical reactions involve only an interchange of atoms or ions between reactants, or perhaps only the dissociation of one reactant into two parts. In such reactions, there is no change in the electrical charge of any of the atoms involved. This chapter deals with another type of reaction, in which one or more electrons are transferred between atoms, with the result that some of the atoms involved do have their electrical charges changed. These reactions are known as electron-transfer reactions. You can appreciate their importance when you realize that every battery used in electronic devices and machines, every impulse involved in nerve transmission, every metabolic reaction that produces energy in biological systems, photosynthesis, and combustion processes (to mention but a few examples) requires electron-transfer reactions. 

Photosynthesis occurs only in plants, algae, and some bacteria, but all forms of life are dependent on its products. In photosynthesis, electromagnetic energy from the sun is used as the driving force for a thermodynamically unfavorable chemical reaction, the synthesis of carbohydrates from C02 and H20 (Equation E9.1). 

The photosynthetic process in green plants occurs in subcellular organelles called chloroplasts. These organelles resemble mitochondria they have two outer membranes and a folded inner membrane called the thy-lakoid. The apparatus for photosynthesis, including the chlorophyll reaction centers and electron carriers, is in the thylakoid membrane. The chemical reactions of the Calvin cycle take place in the stroma, the region around the thylakoid membrane. 

Electron transfer between two molecules, e.g. M and N, is one of the most fundamental and widespread of all photoinduced chemical reactions. It is at the basis of photosynthesis (section 5.1) in nature, and of photography (section 6.1) in industrial applications. 

The overall chemical reaction of photosynthesis (of green plants for instance) is the combination of water and carbon dioxide to form saccharides, or polysaccharides... 

The electron localized on the particle Q is subsequently used, through a complicated chain of chemical reactions, to reduce C02 to the carbohydrates (CH20)6, while the "hole localized on the particle C+ is used to oxidize some certain substrate, say hydrogen sulphide to sulphur. This results in the regeneration of the active centre C-P-J-A-Q. The overall chemical reaction of photosynthesis in purple bacteria can be thus written as... 

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