Essential for Life

The manganese content of soils can vary widely. A deficiency in most crops is indicated by an overall chlorosis (chlorophyll deficiency), e.g. gray spots on the leaves of oats. In such cases manganese sulfate provides an efficient remedy. 

Manganese is essential to ensure the health of humans and animals, and the human body contains about 14 mg manganese. Manganese deficiency leads to different diseases, including impaired growth and depressed reproductive functions. A dietary uptake of 3 mg/day seems to be necessary. Nuts, cereals, dried fruits, meat, fish and seafood are important sources. A curiosity is that tea is very rich in manganese, ten times more than cereals. 

2 Carl Wilhelm Scheele, About Braunstein or Magnesia and its properties [Om Brun-sten eller Magnesia och dess egenskaper], in Swedish, Transactions of The Royal Swedish Academy of Sciences, 1774, pp. 89-116 and 177 194 

(in Swedish), Transactions of The Royal Swedish Academy of Sciences, 1785,141-158 

Thomas S. )ones. Manganese chapter in Mineral Commodity Summaries 2002, USGS, Reston, VA, pp. 104-105, and Manganese chapter in U.S. Geological Survey Minerals Yearbook 2000, Vol. 1, Metals and Minerals, USGS, Reston, VA, pp. 50.1-50.10 

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Selected physical properties of oxygen are included in Table 9.24. It is a colourless, odourless and tasteless gas which is essential for life and considered to be non-toxic at atmospheric pressure. It is somewhat soluble in water and is slightly heavier than air. Important uses are in the steel and glass industries, oxyacetylene welding, as a chemical intermediate, waste-water treatment, fuel cells, underwater operations and medical applications. 

We all have needs, requirements, wants, and expectations. Needs are essential for life, to maintain certain standards, or essential for products and services, to fulfill the purpose for which they have been acquired. Requirements are what we request of others and may encompass our needs but often we don t fully realize what we need until after we have made our request. For example, now that we own a mobile phone we discover we really need hands-free operation when using the phone while driving a vehicle. Hence our requirements at the moment of sale may or may not express all our needs. Our requirements may include wants - what we would like to have but do not need nice to have but not essential. Expectations are implied needs or requirements. They have not been requested because we take them for granted - we regard them to be understood within our particular society as the accepted norm. They may be things to which we are accustomed, based on fashion, style, trends, or previous experience. Hence one expects sales staff to be polite and courteous, electronic products to be safe and reliable, policemen to be honest, etc. 

This series in heterocychc chemistry is being introduced to collectively make available critically and comprehensively reviewed hterature scattered in various journals as papers and review articles. All sorts of heterocyclic compounds originating from synthesis, natural products, marine products, insects, etc. will be covered. Several heterocyclic compounds play a significant role in maintaining life. Blood constituents hemoglobin and purines, as well as pyrimidines, are constituents of nucleic acid (DNA and RNA). Several amino acids, carbohydrates, vitamins, alkaloids, antibiotics, etc. are also heterocyclic compounds that are essential for life. Heterocyclic compounds are widely used in clinical practice as drugs, but all applications of heterocyclic medicines can not be discussed in detail. In addition to such applications, heterocyclic compounds also find several applications in the plastics industry, in photography as sensitizers and developers, and the in dye industry as dyes, etc. 

Biocatalysts these are essential for life and play a vital role in most processes occurring within the body as well as in plants. In the laboratory biocatalysts are usually natural enzymes or enzymes produced in situ from whole cells. They offer the possibility of carrying out many difficult transformations under mild conditions and are especially valuable for producing enantiomerically pure materials. Their huge potential is currently largely untapped, partially due to the time and expense of isolating and screening enzymes. 

Start with water, which is essential for life as we know it. If the water molecule were linear rather than bent, it would lack the properties that life-forms require. Linear water would not be polar and would be a gas like carbon dioxide. Why is water bent Its four electron pairs adopt tetrahedral geometry, putting lone pairs at two vertices of a tetrahedron and hydrogen atoms at the other two vertices. 

Iodine is incorporated in thyroid proteins to form thyroxin and 3-I-thyroxine, both hormones essential for life. They are determined by immunochemical methods. Deficiency of I may lead to crop disease. 

Attention — this is not a textbook It is also not meant to replace one. Nevertheless, there is a lot to be learnt, albeit in a different manner from that in which chemistry is normally presented. The initial question is old and simple "What does the world consist of " This leads to the next question "Who were the researchers who discovered this " They should not be forgotten by us, who take almost for granted all the advantages of progress. After all, the discovery of the 92 elements that occur in the universe and that can also be found on Earth is one of the greatest accomplishments of human intellectual curiosity. Through these discoveries we know what stars are made of, we know the composition of the Earth, and we know which elements are essential for life. 

Many substances which are necessary (and even essential) for life functions contain sulphur for example, the amino acids cysteine and methionine, the tripeptide glutathione or coenzyme A (CoA), with the latter containing the SH group of cys-teamine as the terminal functional group. CoA acts as a coenzyme in all important biochemical acylations. The cysteamine SH group bonds to carboxylic acids to give thioesters ... 

Trace amounts of copper are essential for life. However, as with iron, excess copper is also toxic, on account of its capacity to catalyse the Fenton reaction. There are analogies and differences between these two elements successively selected by Nature as it was obliged to adapt life to the first general irreversible pollution of the earth, namely the advent of dioxygen. 

A reaction of carbon dioxide that is essential for life forms is that of photosynthesis in which C02 is converted by plants into glucose. The process can be summarized as... 

Phytochemicals or phytonutrients are bioactive substances that can be found in foods derived from plants and are not essential for life the human body is not able to produce them. Recently, some of their characteristics, mainly their antioxidant capacity, have given rise to research related to their protective properties on health and the mechanisms of action involved. Flavonoids are a diverse group of phenolic phytochemicals (Fig. 6.1) that are natural pigments. One function of flavonoids is to protect plants from oxidative stress, such as ultraviolet rays, environmental pollution, and chemical substances. Other relevant biological roles of these pigments are discussed in other chapters of this book. 

The term vitamin is a misnomer, the name means vital amines, and while vitamins are essential for life they are not, as was originally supposed, amines. Most vitamins were discovered as a result of a deficiency disease produced by a restricted diet. Long voyages on sailing ships with a diet composed of ship s biscuit, dried beans, dried peas and salted meat produced scurvy. In the worst cases the whole crew were affected, but the ship s officers tended to be less severely affected. 

Iron is essential for life and is required for many different types of iron-containing proteins. Microbes and other organisms go to extraordinary lengths to acquire Fe. Many microbes secrete specific and high affinity Fe chelators known as siderophores. More than 200 are known in bacteria alone (Neilands 1981). Siderophores overcome the problem of the low solubility of Felll especially in oxidising environments, and... 

The major elements phosphorus and sulfur and the trace elements sodium, potassium, magnesium, calcium, chlorine, iodine, manganese, iron, cobalt, nickel, copper, and zinc, and a few others, play specific, critical roles in life. Several others occur in living systems but may not be essential for life. 

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