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| {{Image|Muncprotein.jpg|right|300px|Inman M ( ) Shape of a common protein module suggests role as molecular switch.}} | | {{:{{FeaturedArticleTitle}}}} |
| '''[[Macromolecular chemistry]]''' is the study of the physical, biological and chemical structure, properties, composition, and reaction mechanisms of [[macromolecules]]. A macromolecule is a molecule that consists of one or more types of repeated 'building blocks'. The building blocks are called [[Monomer|monomeric unit]]s (monomers).
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| Macromolecules (also known as polymer molecules) appear in daily life in the form of [[plastic]], [[styrofoam]], [[nylon]], etc. These [[polymer]]s, i.e., substances consisting of polymer molecules, are of great technological importance and are used in the manufacturing of all sorts of goods, from automobile parts to household appliances. The artificial polymer molecules usually exist of long repetitions of identical monomers, either in chains or networks.
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| In molecular biology macromolecules (biopolymers) play a very important role: the well-known molecules [[DNA]], [[RNA]], and [[polypeptides]] ([[proteins]]) are examples of macromolecules. In molecular biology one is mostly interested in macromolecules in solution, usually dissolved in water. The biological function of macromolecules in living cells is a highly relevant and widely studied topic of research. Although, strictly speaking, biopolymers belong to the class of polymer molecules, there is a tendency not to use the latter name in biological applications, but to speak of macromolecules. The term "polymer" is usually reserved for the substances manufactured in bulk by the chemical industry.
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| In industry, the value of synthetic macromolecules as plastics and nylon, has risen enormously over the last 60 years. They have made it possible to mould shapes that would have been impossible to create without them. When they were first developed, their resistance to rupture and degradation was seen as a profound advantage, but nowadays we seek more biologically degradable plastics such as polyethyleneglycol that pollute the environment less.
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| Biological macromolecules include, besides the molecules already mentioned, [[enzyme]]s, and [[polysaccharide]]s, such as cellulose and starch. The better understanding of the basic behavior of polymer molecules has enhanced our knowledge of these biological molecules, and studies of partially charged [[polyelectrolytes]] have led to a deeper insight into their biological function. The investigations of the three-dimensional structure of macromolecules, (their [[configuration]] and [[conformation]]), have led to the identification of specific regions that perform specialized activities. A good example is the catalytic role of particular amino acid residues in polypeptide enzymes and the role of [[functional group]]s such as [[biotin]] or [[riboflavin]] in cellular metabolism. The folding of macromolecules is now a topic of much scientific investigation, since the correct folding of these polymers is a critical factor for normal function. Abnormal folding of particular proteins is the cause of several diseases, including [[Alzheimer disease|Alzheimer's]] and [[Creutzfeldt-Jakob disease]] (CJD) .
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Latest revision as of 09:19, 11 September 2020
The Mathare Valley slum near Nairobi, Kenya, in 2009.
Poverty is deprivation based on lack of material resources. The concept is value-based and political. Hence its definition, causes and remedies (and the possibility of remedies) are highly contentious.[1] The word poverty may also be used figuratively to indicate a lack, instead of material goods or money, of any kind of quality, as in a poverty of imagination.
Definitions
Primary and secondary poverty
The use of the terms primary and secondary poverty dates back to Seebohm Rowntree, who conducted the second British survey to calculate the extent of poverty. This was carried out in York and was published in 1899. He defined primary poverty as having insufficient income to “obtain the minimum necessaries for the maintenance of merely physical efficiency”. In secondary poverty, the income “would be sufficient for the maintenance of merely physical efficiency were it not that some portion of it is absorbed by some other expenditure.” Even with these rigorous criteria he found that 9.9% of the population was in primary poverty and a further 17.9% in secondary.[2]
Absolute and comparative poverty
More recent definitions tend to use the terms absolute and comparative poverty. Absolute is in line with Rowntree's primary poverty, but comparative poverty is usually expressed in terms of ability to play a part in the society in which a person lives. Comparative poverty will thus vary from one country to another.[3] The difficulty of definition is illustrated by the fact that a recession can actually reduce "poverty".
Causes of poverty
The causes of poverty most often considered are:
- Character defects
- An established “culture of poverty”, with low expectations handed down from one generation to another
- Unemployment
- Irregular employment, and/or low pay
- Position in the life cycle (see below) and household size
- Disability
- Structural inequality, both within countries and between countries. (R H Tawney: “What thoughtful rich people call the problem of poverty, thoughtful poor people call with equal justice a problem of riches”)[4]
As noted above, most of these, or the extent to which they can be, or should be changed, are matters of heated controversy.
- ↑ Alcock, P. Understanding poverty. Macmillan. 1997. ch 1.
- ↑ Harris, B. The origins of the British welfare state. Palgrave Macmillan. 2004. Also, Oxford Dictionary of National Biography.
- ↑ Alcock, Pt II
- ↑ Alcock, Preface to 1st edition and pt III.
