Essential Chemical Elements

Bioinorganic Chemistry A Short Course, Second Edition, by Rosette M. Roat-Malone Copyright 2007 John Wiley Sons, Inc. 

Considering the content of earth s contemporary waters and atmospheres, many questions arise as to the choice of essential elements at the time of life s origins 3.5 billion or more years ago. Certainly, sufficient quantities of the bulk elements were available in primordial oceans and at shorelines. However, the concentrations of essential trace metals in modern oceans may differ considerably from those found in prebiotic times. Iron s current approximate 10 mM 

TABLE 1.1 Percentage Composition of Selected Elements in the 1111 ill an Body 

Element Percentage (by weight) Element Percentage (by weight) 

Sodium, potassium, sulfur 0.10 Selenium, manganese, arsenic, nickel 2. X 10-  

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In addition to essentiality, chemical elements and compounds found in biological systems obey homeostatic criteria. Homeostasis, the maintenance of chemical elements and compounds at optimal physiological levels, is a complex interactive system involving many elements and the biological energy supply. Interactions... 

Figure 2. Dependence of biochemical and physiological processes in organisms on the content of essential chemical elements in the biogeochemicalfood webs as a physiological adaptation curve. 1—lower (deficient) content 2—optimum content 3—excessive (upper) content.

Fig. 1.1 Network of interactions/influences among some essential chemical elements in plants (Kaim and Schwederski 1993). The parameter used for attribution of either synergy or antagonisms to an interelement relationship is rate of plant growth...

However, our interest is focused with the set of (possibly essential) chemical elements which can be absorbed in different speciation forms (e.g. N as NH +, nitrate, urea or even unchanged glycine (Bardgett 2005)), neglecting these very speciation forms, which simplifies Eq. 2.22a to yield... 

The basic idea to remember, for your health s sake, is that we are made of the minerals and trace elements present in the soil, and unless the foods we eat are grown on rich, fully mineralized soil, our bodies will become deficient in one or more essential chemical elements, and we will become vulnerable to a disease. I don t deny that we also need exercise, fresh air, and enough rest to have healthy bodies, but our focus in this book will be on foods, the chemical elements in them, and how they are used in our bodies. If you learn about foods and the nutrients in them, the other aspects of a healthy lifestyle will tend to make more sense and fall into place in your understanding. 

Bones not only provide structure to our bodies, but they act as warehouses holding reserves of essential chemical elements. Any excess of essential chemical elements in the blood... 

Compare the fluxes and pools of essential chemical elements in Boreal Forest and Tropical Rain Forest ecosystems. Explain the reasons for the intensive rates of biogeochemical turnover in tropical forests. 

Figure 2. The essential chemical element for the two classes of photosystem II inhibitors...

Table 1. Chemical Elements Essential to Healthy Growth of Plants ...

Devising an economical method of producing agricultural-grade potassium phosphates from potassium chloride and wet-process phosphoric acid has been the subject of intense agricultural—chemical research (37—39). Limited quantities have been produced industrially. The impact on the overall quantities of phosphoms and potassium compounds consumed by the fertilizer industry is small. Because potassium phosphates are an excellent source of two essential fertilizer elements, this research is expected to continue. 

It IS the stantng material for the preparation of nearly all manganese chemicals and is used m tenilizers tn arca.s of the world where there is a deficiency of Mn in the soil, since Mn is an essential irace element in plani growth. The anhydrous salt has a surprising Ihermal siabiliiy it remains unchanged even at red heal, whereas the solfates of Fe , Co" and Ni" all decompose under these conditions. 

A shortage of any of some two dozen chemical elements that are essential for the growth of organisms can reduce ecosystem productivity, but phosphorus and nitrogen are often the most limiting nutrients, which is why these two elements are standard components of commercial fertilizers. Phosphorus is often limiting because it moves through soil pores and aquatic... 

Not surprisingly, only about 20 of the chemical elements found on Earth are used by living organisms (Chapters 3 and 8). Most of them are common elements. Rare elements are used, if at all, only at extremely low concentrations for specialized functions. An example of the latter is the use of molybdenum as an essential component of nitrogenase, the enzyme that catalyzes the fixation of elemental dinitrogen. Because they are composed of common elements, living organisms exert their most profound effects on the cycles of those elements. 

Life processes ultimately depend on the transport and reactivity of chemical elements and compounds. Modern biological studies have elegantly unraveled the complicated carbon-based metabolic cycles that are essential to the maintenance of many living things. 

Fertilizers are immensely important to humanity. Agriculture requires fertilizers because growing plants remove various chemical elements from the soil. In a fully contained ecosystem, decaying organic matter replenishes the soil, but the elements contained in crops that are harvested and shipped elsewhere are not replenished. Thus, intensive agriculture inevitably depletes the soil of essential elements, which must be replaced by fertilization. 

The noble gas elements act as a record of the deposited material because they are essentially chemically inert and are also trapped within the ice of comets and meteorites. The late-heavy bombardment era must have affected both the Earth and the Moon similarly so an estimate of the collision frequency may be obtained by using the record of impacts on the Moon s surface. The collision rate calculated... 

Chemical elements essential to life forms can be broken down into four major categories (1) bulk elements (H, C, N, O, P, S) (2) macrominerals and ions (Na, K, Mg, Ca, Cl, PO4A SC>4 ) (3) trace elements (Fe, Zn, Cu) and (4) ultratrace elements, comprised of nonmetals (F, I, Se, Si, As, B) and metals (Mn, Mo, Co, Cr, V, Ni, Cd, Sn, Pb, Li). The identities of essential elements are based on historical work and that done by Klaus Schwarz in the 1970s.1 Other essential elements may be present in various biological species. Essentiality has been defined by certain... 

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