Metabolic activities

This is also highly important, as in the case of DDT and dieldrin. If the metabolic rate is very slow, the organisms in lower tropic levels will have little time to dispose of the pesticide before they are consumed by those in high tropic levels. 

---

Table 2. Examples of Metabolic Detoxification and Metabolic Activation of Chemicals by Biological Systems...

Physiological or biochemical changes have been observed in plants exposed to air pollutants, including alterations in net photosynthesis, stomate response, and metabolic activity. Such exposure studies have been conducted under controlled laboratory conditions. An understanding of the processes involved will help to identify the cause of reduction in yield. 

Viable cells mean cells which can grow non-viable cells mean cells which cannot. Microbiologists use the same terms but can divide non-viable cells into cells, which remain metabolically active in some respects and cells which are effectively dead. They can also distinguish within their category of "viable cells between cells, which are actively dividing, and cells such as spore cells whose growth activities are potential rather than actual. 

The consequence of the relationships of Table 5.3 and Fig. 5.2 is that for a neutral thermal sensation, at steady state, the core temperature increases while the skin temperature decreases with increased metabolic activity (Fig. 5.3). The increase in metabolism causes sweating which decreases skin tem-perature. 

The interactions may be physicochemical without the participation of biological mechanisms for example, deep lung exposure to highly soluble irritative gases, such as sulfur dioxide, may become enhanced due to adsorption of the gas onto fine particles. Biological interactions may occur at all stages and body sites. For example, toxicity is increased when adverse effects are due to some reactive metabolic intermediate and exposure to another agent stimulates its metabolic activation (enzyme induction). 

Covalent binding of chemicals to biological macromolecules can also cause toxicity. During biotransformation and metabolic activation, chemical compounds can be changed to free radicals, which have an unpaired... 

Metabolic rate (M) The rate of transformation of chemical energy into heat and mechanical work by aerobic and anaerobic metabolic activities w ithin an organism, usually expressed per unit area of the total body surface, in met or W m -. 

If the plasma pH is 7.4 and the plasma concentration of HCOa is 15 mM, what is the plasma concentration of H9CO3 What is the plasma concentration of CO9(dissolved t If metabolic activity changes the concentration of CO9(dissolved to 3 mM, and [HCOa ] remains at 15 mM, what is the pH of the plasma ... 

In addition, adenosine is implicated in sleep regulation. During periods of extended wakefulness, extracellular adenosine levels rise as a result of metabolic activity in the brain, and this increase promotes sleepiness. During sleep, adenosine levels fall. Caffeine promotes wakefulness by blocking the interaction of extracellular adenosine with its neuronal receptors. ... 

Nitrogen oxides are generated by both human and nonhuman action, but the major sources of NO, are high-temperature combustion processes such as those occurring in power plants and automobile engines. Natural sources of NO., include lightning, chemical processes that occur in soil, and the metabolic activities of plants. 

For type 3 processes, growth and metabolic activity reach a maximum early in the batch process cycle (Figure 3.1) and it is not until a later stage, when oxidative activity is low, that maximum desired product formation occurs. The stoichiometric descriptions for both type 3 and 4 processes depend upon the particular substrates and products involved. In the main, product formation in these processes is completely uncoupled from cell growth and dictated by kinetic regulation and activity of cells. 

This discrepancy is due to die fact that other products such as formate, are formed in very small amounts as byproducts of the metabolic routes leading to L-phenylalanine and polymer synthesis. Of course, part of die glucose is also used for die metabolic activities in the micro-organism necessary to maintain the cells in a viable state, this is termed the maintenance energy requirement... 

Cell growth and metabolic activities are similarly described as a simple chemical reaction. It is also necessary to establish a definite formula for dry cell matter. The elemental composition of certain strains of microorganism is defined by an empirical formula CHaO/3Ns. The general biochemical reaction for biomass production is based on consumption of organic substrate, as shown below. Substrate oxidation is simplified in the following biochemical oxidation ... 

Gemcitabine (Fig. 7) is a cytosine derivative that is very similar to ara C. It undergoes metabolic activation to difluorodeoxycytidine triphosphate, which interferes... 

A prodrag is a drug that is not by itself pharmacologically active but needs metabolic activation by an enzyme. Examples are the cytostatic cyclophosphamide, which is activated by hydroxylation catalyzed by CYP2B6, or HMGCoA reductase inhibitor, lovastatin, which contains... 

The composition of body fluids remains relatively constant despite the many demands placed on the body each day. On occasion, these demands cannot be met, and electrolytes and fluids must be given in an attempt to restore equilibrium. The solutions used in the management of body fluids discussed in this chapter include blood plasma, plasma protein fractions, protein substrates, energy substrates, plasma proteins, electrolytes, and miscellaneous replacement fluids. Electrolytes are electrically charged particles (ions) that are essential for normal cell function and are involved in various metabolic activities. This chapter discusses the use of electrolytes to replace one or more electrolytes that may be lost by the body. The last section of this chapter gives a brief overview of total parenteral nutrition (TPN). 

Although it is possible to identify a group of particularly toxic components in venom, it should be noted that the venoms are complex mixtures of components, many of which are synergistic. Muscle damage is particularly severe if myotoxic activity is combined with hemorrhagic activity. In this case, muscle regeneration is impaired, because the regenerating tissue is rendered anoxic at a time of intense metabolic activity. 

---