Functional biochemistry, examples

Vitamin biochemistry is a fascinating topic of knowledge. Many of the functions of "the vitamins," as revealed in this chapter, also take place in plants, bacteria, and archae. However, those interesting in delving deeper will be delighted to Icam about further functions of "the vitamins" that take place in these life forms. One of the stranger functions, for example, is the role of folates as a structural component in some bacterial viruses. 

The sections below deal with the biochemistry of the Ca " " ion only insofar as it is involved in catalysis (i.e. enzymatic activity.) They will not deal with Ca " bound to enzymes in which this ion plays a purely passive structural role as in the case of the Zn " " endoproteinase thermolysin which binds a Zn " " ion at the active site and four Ca ions elsewhere which stabilize the structure . Removal of the Ca " " causes this enzyme to autolyze (self-digest) and become inactive, but Ca is not directly involved in the catalytic function. Many examples of Ca acting in a passive structural rule are known. ... 

As an example, bulk modification by the organic reaction of unsaturated PHA with sodium permanganate resulted in the incorporation of dihydroxyl or carboxyl functional groups [106]. Due to the steric hindrance of the isotactic pendant chains, complete conversion could not be obtained. However, the solubility of the modified polymers was altered in such a way that they were now completely soluble in acetone/water and water/bicarbonate mixtures, respectively [106]. Solubility can play an important role in certain applications, for instance in hydrogels. Considering the biosynthetic pathways, the dihydroxyl or carboxyl functional groups are very difficult to incorporate by microbial synthesis and therefore organic chemistry actually has an added value to biochemistry. 

M. Buck reviews in great depth the literature on self-assembled monolayers (SAMs) of thiols on gold, a classic means of surface modification. The wide variety of functional groups that is provided by synthetic chemists makes thiol-SAMs an exciting playground for applications where the gap between two worlds, the inorganic and the organic, needs to be closed. Examples are molecular electronics and biochemistry. 

Our study of heterocyclic compounds is directed primarily to an understanding of their reactivity and importance in biochemistry and medicine. The synthesis of aromatic heterocycles is not, therefore, a main theme, but it is useful to consider just a few examples to underline the application of reactions we have considered in earlier chapters. From the beginning, we should appreciate that the synthesis of substituted heterocycles is probably not best achieved by carrying out substitution reactions on the simple heterocycle. It is often much easier and more convenient to design the synthesis so that the heterocycle already carries the required substituents, or has easily modified functions. We can consider two main approaches for heterocycle synthesis, here using pyridine and pyrrole as targets. 

This diversity of mental retardation, in both cause and phenotype, carries important implications for consideration of the biochemistry of consciousness. On the one hand, because this is an investigation of multiple causalities—including, for example, inborn errors of metabolism, each of which has its own unique biochemical profile (Cook Leventhal, 1996), it may not prove possible to identify specific neurotransmitter abnormalities which are common to mental retardation as such. On the other hand common themes concerning key neurotransmitters may be identified from studies of mental retardation. Altered neurotransmitter functioning associated with the severity of mental retardation is open to different interpretations, either reflecting fundamentally impaired development of cerebral structure or a more general impairment of central transmitter activity and functioning. 

Nature is economical in her means. She uses many of the same chemicals to accomplish her nervous purposes within the brain that she has already used to the same ends throughout the body. The good news is that once you have worked out the biochemistry and pharmacology of a neuromodulator in the body, you can apply a lot of what you know to its action in the brain. The bad news is that every time you target, for example, the acetylcholine system of the brain, you also hit the body. That means that the heart, the bowel, the salivary glands, and all the rest of the organs innervated by the autonomic nervous system are influenced. What is worse, the target sites within the brain may not only be as spatially dispersed as in the periphery, but may also be as functionally differentiated ... 

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