Alcohol metabolism processes

MRS research is increasingly used to indicate the regions of brain affected in addiction/alcoholism 943 MRS can provide a snapshot into the metabolic processes of brain tumors 944... 

Alcohol impairs some metabolic processes, including gluconeogenesis which, in some conditions, is an essential process for wellbeing and normal behaviour (Chapters 6 and 14). 

Severe thiamine vitamin Bf) deficiency results in beriberi. The symptoms can include growth retardation, muscular weakness, apathy, edema, and heart failure. Neurological symptoms, such as personality changes and mental deterioration, also may be present in severe cases. Because of the role played by thiamine in metabolic processes in all cells, a mild deficiency may occur when energy needs are increased. Since thiamine is widely distributed in food, beriberi is rare except in communities existing on a single staple cereal food. The disease does occur with some frequency in alcoholics, whose poor diet may lead to an inadequate daily intake of thiamine. 

Two major pathways of alcohol metabolism to acetaldehyde have been identified (Figure 23-1). Acetaldehyde is then oxidized to acetate by a third metabolic process. 

This is known as Michaelis-Menten or saturation kinetics. The processes that involve specific interactions between chemicals and proteins such as plasma protein binding, active excretion from the kidney or liver via transporters, and metabolism catalyzed by enzymes can be saturated. This is because there are a specific number of binding sites that can be fully occupied at higher doses. In some cases, cofactors are required, and their concentration may be limiting (see chap. 7 for salicylate, paracetamol toxicity). These all lead to an increase in the free concentration of the chemical. Some drugs, such as phenytoin, exhibit saturation of metabolism and therefore nonlinear kinetics at therapeutic doses. Alcohol metabolism is also saturated at even normal levels of intake. Under these circumstances, the rate of... 

During alcohol metabolism, NAD+ becomes unavailable to the many other vital body processes for which it is needed, including glycolysis, the TCA cycle and the mitochondrial respiratory chain. Without NAD+, the energy pathway is blocked and alternative routes are taken, with serious physical consequences ... 

While there are very many good examples of oxidation-reduction processes in nature, perhaps the two most classic examples are aerobic respiration and alcohol metabolism by the liver, each of which is considered briefly in turn here. 

The ethylene glycol and methyl alcohol (see below), which is also sometimes found in antifreeze, are poisonous because they are converted into more toxic products. Once inside the body, the ethylene glycol in the antifreeze is changed by metabolism into first one, and then several other chemicals. This requires the same enzyme that metabolizes the alcohol we consume in alcoholic drinks (ethyl alcohol). The ethylene glycol is converted into oxalic acid which is poisonous, and other poisonous products are also produced. Oxalic acid is also found in rhubarb leaves, which is what makes them poisonous. The result of these metabolic conversions is that the acidity of the blood increases (the pH decreases) and normal metabolic processes are inhibited. The oxalic acid formed can crystallize in the brain and the kidneys, causing damage. The oxalic acid also reacts with calcium and removes it from the body. The reduction of calcium... 

After we have had a drink, the alcohol it contains is absorbed into the blood and enters the liver, where it is broken down by an enzyme (alcohol dehydrogenase) into a chemical called acetaldehyde. This is formed slowly, fortunately (as it is responsible for some of the unpleasant effects of alcoholic drinks, flushes, headache, nausea). Thankfully, it is also removed more rapidly by another enzyme (aldehyde dehydrogenase), to form acetic acid, which is then incorporated into normal metabolic processes, to produce energy for the body for example. 

Biological metabolic processes attack most of the sugar alcohols studied. 

Molds while growing produce various chemicals as a result of their primary metabolic processes. These processes are needed to ensure the continuation of the mold s life cycle. The gaseous metabolic products are collectively referred to as microbial volatile organic compounds (mVOCs). Some mVOCs are primary solvents and are chemically identical to those originating from solvent-based building materials and cleaning supplies (e.g., alcohols, aldehydes, ketones, hexane, methylene chloride, benzene, and acetone). 

Reactions of oxidoreduction are an example of chiral inversion that takes place by the intermediacy of two opposing metabolic processes. The alcohol/ketone equilibrium mediated by alcohol dehydrogenase enzyme is an abundant reaction. The dehydrogenation of secondary alcohols to a ketone proceeds with substrate stereoselectivity in oxidation, while the hydrogenation of the ketone metabolite is product selective to one face of the carbonyl group. The consequence of the metabolism of the secondary alcohols may involve chiral inversion of this center, which can result in an altered proportion of the two enantiomers or epimers. 

Fermentation itself can be stopped when the desired alcohol content is reached, either by removal of yeast (filtration, centrifugation) or by their deactivation (pasteurization). A further possibility is to create fermentation conditions, which suppress yeast metabolism (Narziss, Miedaner, Kem, Leibhard, 1992). The most practical tool to suppress yeast metabolism is low temperature. This method is called the cold contact process (CCP) , which ensures very slow ethanol prodnction while other metabolic processes, snch as formation of higher alcohols and esters or reduction of carbonyls, may exhibit moderate activities (Perpete Collin, 1999). After interrupting the fermentation at an alcohol content less than 0.5% voL, the AFB is usually matured for at least 10 days at 0-1 °C to enrich flavour and improve the colloidal stability. Then the product is filtered, carbonated, stabilized and sterilized (Branyik, Silva, et al., 2012 Burberg Zamkow, 2009). 

The electric oscillations of the brain make themselves evident in a crude way in electroencephalograms, which show patterns of electric oscillation that depend upon the state of consciousness and the nature of the encephalonic activity of the subject. Evidence that the ephemeral memory, with an effective life that is rarely longer than a few minutes, is electrical in nature is provided by a number of observations. It has been noted that unconsciousness produced by a blow to the head or electric shock often has caused complete loss of memory of the events experienced during the period of 10 or IS minutes before the blow or shock to the brain. Moreover, when the formation of new permanent memories is interfered with by the decreased ability of the brain to carry on metabolic processes involving proteins, as in old age or KorsakolTs syndrome (alcoholism, protein starvation, thiamine deficiency), the memory continues for a period of 10 or IS minutes, but usually not much longer the memory seems to persist only so long as conscious attention is directed to it (3). 

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