Biochemical reaction, location

Under the diffusive laminar flow conditions, the ability to add reagents at specific locations or times leads to the unique ability to control and monitor the spatial and temporal domain of dynamic chemical processes. This attribute has some analogies with the control exerted on biochemical reactions by the micron-scale structures of living cells. Ex-... 

Almost all enzymes are proteins. They provide templates whereby reactants (substrates) can bind and are favorably oriented to react and generate the products. The locations where the substrates bind are known as active sites. Because of the specific 3D structures of the active sites, the functions of enzymes are specific that is, each particular type of enzyme catalyzes specific biochemical reactions. Enzymes speed up reactions, but they are not consumed and do not become part of the products. Enzymes are grouped into six functional classes by the International Union of Biochemists (Table 2.2). 

Enzymatic reactions can be impeded by the addition of exogenous molecules. This is how drugs are used to control biochemical reactions, and most drugs are used for inhibitory functions. Drugs may function as competitive inhibitors or as noncompetitive inhibitors. Competitive inhibitors compete with the substrates for binding to the active sites, whereas noncompetitive inhibitors bind to another location (allosteric site) but affect the active site and its consequential interactions with the substrates. Some drugs used as enzyme inhibitors are the following ... 

Gyclodextrin cavities form the early models of host molecules involved in supramolecular assemblies. There are many other molecules known as cryptands which can be designed to offer a cavity of fairly precise dimensions to accommodate various ions or metal complexes. It may be possible to locate not just one, but two, guest molecules inside a cryptand cavity, and this may lead to new electron transfer reactions in restricted environments another step towards synthetic photoinduced biochemical reactions. 

The second main class of blood constituents used as genetic markers are the polymorphic enzymes. The enzymes of interest to the forensic serologist are primarily located within the red blood cell and are commonly referred to as isoenzymes. These can briefly be described as those enzymatically active proteins which catalyze the same biochemical reactions and occur in the same species but differ in certain of their physicochemical properties. (This description does not exclude the tissue isoenzymes that occur within the same organism however, our consideration deals only with those of the red blood cell in particular.) The occurrence of multi-molecular forms of the same enzyme (isoenzymes) has been known for several decades however, it was not until the Metropolitan Police Laboratory of Scotland Yard adapted electrophoretic techniques to dried blood analysis that these systems were catapulted to the prominence they presently receive (.2). For many of the forensic serologists in the United States, the use of electrophoresis and isoenzyme determination is a recently-inherited capability shared by only a few laboratories. 

Ascorbic acid is a vitamin in primates. In most other animals, it can be synthesized by a branch of the glucoronic acid pathway (Chapter 18). It is apparently not changed into any coenzyme in the human being and participates as a vitamin in a reducing capacity in several biochemical reactions. These include the post-translational hydroxylation of proline in collagen biosynthesis (Chapter 8) and in tyrosine metabolism (Chapter 20). Ascorbic acid is oxidized to dehydroascorbic acid, a diketo derivative of ascorbate. Scurvy is a deficiency disease caused by a shortage of dietary ascorbic acid. In children, this results in defective bone formation in adults, extensive bleeding occurs in a number of locations. Scurvy is to be suspected if serum ascorbic acid levels fall below 1 jug/mL. 

No studies were located regarding levels of acrolein or its metabolites in human tissues and fluids associated with effects. No biochemical or histological changes specific for acrolein exposure were identified. Results from a toxicokinetic study suggested that acrolein can react with proteins and nucleic acids in the organism (Patel et al. 1980). After transformation into acrylic acid, incorporation into amino acids, fatty acids, and sterols can be expected. However, specific effects associated with these biochemical reactions are not known. 

All biochemical reactions are enzyme-mediated. The rate of an enzyme reaction depends on the substrate concentration at the location of the enzyme and thereby on the diffusion rate of a substrate to the enzyme. It is therefore important to permanently obtain an intimate contact between a cell or enzyme and substrate molecules. Additionally, the product generated in the bioreactor has to be extracted because it may under certain conditions inhibit its own production. In some processes there may also be even a prepurification in the bioreactor itself. If living micro-organisms have to be applied, it is necessary to provide sufficient nutrition and respiration gases in case of aerobic fermentation. All other reaction parameters such as temperature, pH-value and reaction time have to be controlled precisely. In many cases (generally with modem processes) the maintenance of microbiological integrity (sterile process) is absolutely mandatory for a successful fermentation. 

In order to carry out most biochemical reactions, metalloenzymes generally utilize the rarer transition metal ions. Elements such as zinc, copper, iron, nickel, and cobalt are found in low concentrations in plasma and seawater and yet the enzyme has to select the appropriate metal ion from them. There is evidence for the existence of proteins that can chaperone specific metal ions to their appropriate sites in apoenzymes, protecting the metal ions from adverse reactions as they are guided to their required location [5]. How does the enzyme attempt to select out the one metal ion it requires The answer is that the chemistry of the metal ion is used as a basis for selection. Each metal ion has some property that is different from that of most others, but, in fact, there is often considerable overlap in these properties so that a given enzyme may bind one of several different cations in one specific site. Some relevant data are provided in Tables 1 and 2. The metalloenzyme contains within its overall design an arrangement of preferred side-chain functional groups with the correct size hole to bind the required metal ions in an appropriate hydrophobic or hydrophilic environment. Thus the metalloenzyme binds metal ions... 

Some relatively pure liquids recovered from the environment can be distilled or rereflned and reused. For example, petroleum products recovered from some waste sludge by thermal desorption or waste oils collected from automobiles can be rerefined to make a usable product. The potential to recover usable product from material spilled into the environment can be limited, however. Once spilled, a solvent or petroleum product begins to change physically and chemically. The liquid can become contaminated with water, dirt, or other substances. After some time, chemical and biochemical reactions will alter the chemical composition of the material. Further, the volume recovered from spill cleanup may be relatively small and a rereflning facility may not be located nearby. As a result, it may be more feasible simply to ship the waste for energy recovery. 

Locate measured data on chemical/analogue, including physical/ chemical properties and chemical and biochemical reactions. 

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