Responses metabolism processes

One important point of controversy in risk extrapolation is the existence of the threshold level for carcinogenic and mutagenic response to a pollutant. Some argue that an organism is able to cope with low doses of a substance through metabolic processes or repair mechanisms, so that harmful effects do not appear until a certain minimum threshold, or "safe dose", is surpassed. Others contend that a carcinogenic substance must be considered potentially harmful at any dose, and that even a single molecule may initiate a tumor at the cellular level. This is the so-called "one-hit" hypothesis. 

Nonspecific protein binding to the solid phase complicates the method and is a selective pressure driving its evolution. The adaptive response has been the development of intrinsically comparative methods in which specific binding to an immobilized ligand is blocked in one out of two otherwise identical samples. When the respective protein components of the samples are compared, specifically bound proteins are present in one but severely depleted in the other. To allow relative quantitation, the two samples can be made isotopically distinct by a chemical or metabolic process and then mixed for an analytical step that avoids intersample variability [15]. 

The 5-lipoxygenase pathway of arachidonic acid metabolism is responsible for production of cysteinyl leukotrienes. Leukotrienes C4, D4, and E4 are released during inflammatory processes in the lung and produce broncho-spasm, mucus secretion, microvascular permeability, and airway edema. 

The metabolic machinery responsible for the heterotrophic respiration reactions is contained in specialized organelles called mitochondria. These reactions occur in three stages (1) glycolysis, (2) the Krebs or tricarboxylic acid cycle, and (3) the process of oxidative phosphorylation also known as the electron transport chain. As illustrated in... 

The integrated response to trauma depends on increases in the rates of metabolic processes, which are summarised as follows ... 

Both metabolism and excretion can be viewed as processes responsible for elimination of drug (parent and metabolite) from the body. Drug metabolism changes the chemical structure of a drug to produce a drug metabolite, which is frequently but not universally less pharmacologically active. Metabolism also renders the drug compound more water soluble and therefore more easily excreted. 

It is not known how chemicals cause cancer. A fascinating aspect of the story is that many "carcinogenic" chemicals are in fact, not the culprits responsible for cancer induction. The metabolic processes of the body change the chemicals from relatively innocuous substances into reactive intermediates which in as yet unknown fashion, trigger the chain of events which finally result in tumor formation. In other words, chemical carcinogenesis is an effect of "failed" detoxification. 

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