Photosynthesis component reactions

A method of detecting herbicides is proposed the photosynthetic herbicides act by binding to Photosystem II (PS II), a multiunit chlorophyll-protein complex which plays a vital role in photosynthesis. The inhibition of PS II causes a reduced photoinduced production of hydrogen peroxide, which can be measured by a chemiluminescence reaction with luminol and the enzyme horseradish peroxidase (HRP). The sensing device proposed combines the production and detection of hydrogen peroxide in a single flow assay by combining all the individual steps in a compact, portable device that utilises micro-fluidic components. 

Starch is stored in plant cells in the form of granules in the stroma of plas-tids (plant cell organelles) of two types chloroplasts, in which photosynthesis takes place, and amyloplasts, plastids that are specialized starch accumulation bodies. When starch is to be mobilized and used by the plant that stored it, it must be broken down into its component monosaccharides. Starch is split into its monosaccharide elements by stepwise phosphorolytic cleavage of glucose units, a reaction catalyzed by starch phosphorylase (Figure 7.23). This is formally an a(1 4)-glucan phosphorylase reaction, and at each step, the prod-... 

Rainwater and snowmelt water are primary factors determining the very nature of the terrestrial carbon cycle, with photosynthesis acting as the primary exchange mechanism from the atmosphere. Bicarbonate is the most prevalent ion in natural surface waters (rivers and lakes), which are extremely important in the carbon cycle, accoxmting for 90% of the carbon flux between the land surface and oceans (Holmen, Chapter 11). In addition, bicarbonate is a major component of soil water and a contributor to its natural acid-base balance. The carbonate equilibrium controls the pH of most natural waters, and high concentrations of bicarbonate provide a pH buffer in many systems. Other acid-base reactions (discussed in Chapter 16), particularly in the atmosphere, also influence pH (in both natural and polluted systems) but are generally less important than the carbonate system on a global basis. 

The cations Mg and Ca are major components of bones. Calcium occurs as hydroxyapatite, a complicated substance whose chemical formula is Cas (P04)3 (OH). The structural form of magnesium in bones is not fully understood. In addition to being essential ingredients of bone, these two cations also play key roles in various biochemical reactions, including photosynthesis, the transmission of nerve impulses, and the formation of blood clots. 

Carotenoids protect photosynthetic organisms against potentially harmful photooxidative processes and are essential structural components of the photosynthetic antenna and reaction center complexes. Plant carotenoids play fundamental roles as accessory pigments for photosynthesis, as protection against photooxidation, and... 

Magnesium has its role intimately intertwined with phosphate in many phosphoryl transfer reactions, as Mg-ATP in muscle contraction, in the stabilization of nucleic acid structures as well as in the catalytic activity of ribozymes (catalytic RNA molecules). It also serves as a structural component of enzymes, and is found as the metal centre in chlorophylls, which absorbs light energy in photosynthesis. 

The key feature of photosynthesis is the ability to carry charge spatially away from an excited state reaction centre before the usually highly efficient and biochemically useless recombination can take place. In photosynthetic systems, charge separation occurs about 108 times faster than recombination, a ratio that is impossible to reach in normal chemical reactions. This phenomenon is achieved by the spatial anchoring of the components at particular orientations to one another within a non polar region of the membrane anchored protein, thus preventing free diffusion and allowing a vectorial uphill chemical reaction. 

Photosynthesis The metabolic reactions of green plants (and some other organisms such as certain bacteria) that produce sugars and ultimately other vital components for the plant. Photosynthesis requires sunlight as an energy source and carbon dioxide and produces oxygen as a by-product. 

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