Magnesium photosynthesis

All organisms seem to have an absolute need for magnesium. In plants, the magnesium complex chlorophyll is the prime agent in photosynthesis. In animals, magnesium functions as an enzyme activator the enzyme which catalyses the ATP hydrolysis mentioned above is an important example. 

Preeminent in importance among the macro-cyclic complexes of Group 2 elements are the chlorophylls, which are modified porphyrin complexes of Mg. These compounds are vital to the process of photosynthesis in green plants (see Panel). Magnesium and Ca are also intimately... 

Photopolymerizable coatings relief-image-forming systems, 6,125 Photoreactivity environmental effects, 1, 394 Photoredox properties bipyridyl metal complexes, 2, 90 Photoresist systems, 6,125 Photosensitive materials, 6, 113 Photosynthesis anoxygenic, 6, 589 magnesium and manganese, 6, 588 water decomposition models, 6, 498... 

Magnesium and calcium are by far the most important members of the group. Magnesium is, in effect, the doorway to life it is present in every chlorophyll molecule and hence enables photosynthesis to take place. Calcium is the element of rigidity and construction it is the cation in the bones of our skeletons, the shells of shellfish, and the concrete, mortar, and limestone of buildings. 

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. 

A prime example of this is the crucial ease of such oxidation in the magnesium(II) complex of the chlorin system present in chlorophyll during photosynthesis. Table 8 shows the half-wave potentials for the first ring oxidation of some metalloporphyrins, the examples chosen being based on 5,10,15,20-tetraphenyl porphyrin, TPP (2) and on 1,2,7,8,12,13,17,18-octaethylporphyrin, OEP (16). 

The chlorophyll molecule (309) is involved in initiating photosynthesis in green plants and contains magnesium coordinated to a partially reduced porphyrin (namely, a chlorin derivative). Life relies ultimately on the unique redox and electron transfer abilities of the chlorophylls which are necessary for the conversion of light to chemical energy. Chlorophyll mainly absorbs light from the far red region of the spectrum... 

Reduced photosynthesis in sensitive species (DeNoyelles et al. 1982) Decreased oxygen production, decreased content of calcium and magnesium (Pratt etal. 1988)... 

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. 

Porphyrins 21 are the backbone of major players in life cycles—cytochromes (Scheme 8). There are three types of cytochromes, classified by their color, or more precisely by their long-wavelength absorption band, as a (600 mn), b (563 nm), and c (550 nm). They are protein conjugates of a porphyrin complex with iron(II), which is a coenzyme called heme (22). In plants, porphyrins form a complex with magnesium-(II) chlorophylls a and b (23), vital in photosynthesis. Porphyrin derivatives are used in photodynamic therapy for dermatological diseases such as psoriasis, and for skin or subcutaneous cancer.5c-e... 

Magnesium is an important element that acts as a catalyst in many hfe processes. In addition to photosynthesis, it is also required for the oxidation in animal cells that produce energy and for the production of healthy red blood cells. Humans cannot hve without magnesium— which we acquire mainly from various foods. 

One of the important properties of porphyrins is that they complex with divalent metals, the pyrrole nitrogens being ideally spaced to allow this. Of vital importance to life processes are the porphyrin derivatives chlorophyll and haem. Chlorophyll (actually a mixture of structurally similar porphyrins chlorophyll a is shown) contains magnesium, and is, of course, the light-gathering pigment in plants that permits photosynthesis. 

Magnesium ions in the green pigment chlorophyll are vital to photosynthesis. 

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