Metabolism speed

The term chiral recognition refers to a process m which some chiral receptor or reagent interacts selectively with one of the enantiomers of a chiral molecule Very high levels of chiral recognition are common m biological processes (—) Nicotine for exam pie IS much more toxic than (+) nicotine and (+) adrenaline is more active than (—) adrenaline m constricting blood vessels (—) Thyroxine an ammo acid of the thyroid gland that speeds up metabolism is one of the most widely used of all prescription... 

Diffusion-mediated release of root exudates is likely to be affected by root zone temperature due to temperature-dependent changes in the speed of diffusion processes and modifications of membrane permeability (259,260). This might explain the stimulation of root exudation in tomato and clover at high temperatures, reported by Rovira (261), and also the increase in exudation of. sugars and amino acids in maize, cucumber, and strawberry exposed to low-temperature treatments (5-10°C), which was mainly attributed to a disturbance in membrane permeability (259,262). A decrease of exudation rates at low temperatures may be predicted for exudation processes that depend on metabolic energy. This assumption is supported by the continuous decrease of phytosiderophore release in Fe-deficient barley by decreasing the temperature from 30 to 5°C (67). 

Bioremediation also has its limitations. Some chemicals are not amenable to biodegradation, for instance, heavy metals, radionuclides, and some chlorinated compounds. In some cases, the microbial metabolism of the contaminants may produce toxic metabolites. Bioremediation is a scientifically intensive procedure that must be tailored to site-specific conditions, and usually requires treatability studies to be conducted on a small scale before the actual cleanup of a site.13 The treatability procedure is important, as it establishes the extent of degradation and evaluates the potential use of a selected microorganism for bioremediation. A precise estimate on vessel size or area involved, speed of reaction, and economics can therefore be determined at the laboratory stage. 

The authors are grateful to MD (Molecular Discovery, London, UK www. moldiscovery.com) for the use of the software, and to P. Grossi, B. Speed and P. Crivori (Pharmacia Corporation, Nerviano, Italy), for making available the dataset regarding metabolic stability. 

That the rate of metabolism of several components may be speeded up when they are metabolized together over what would occur if they are acted on separately is also indicated in the increased rate of alcohol... 

The experimental exploration and confirmation of protein functions are relatively slow processes and always require dedicated experiments. The analysis of protein-protein associations as such improved remarkably in quality and speed. This is accompanied by the creation of new databases that will reflect the network of interacting proteins (the Protein Function and Metabolic Pathway project, http //bioinformer.ebi. ac.uk 80/newsletter/archives/4/pfmp.html, and the Biomolecular Interaction Network Database project http //bioinfo.mshri.on.ca/ BIND/). These activities contribute to the idea that cellular mechanisms can be better understood when they are seen as a multicomponent networked process. 

Kinetic parameters Vmax and Km give information about the relative speed of biochemical reactions and the ease of interaction between the enzyme and its substrate respectively. Inhibitors may increase Km or decrease Vmax and metabolic control often relies on these effects. 

Inhibition can be defined as the reduction in the efficiency of an enzyme . Note that the term does not imply that the enzyme is completely non-functional. In fact, the retention of some residual activity is quite important to achieve metabolic control. By analogy, consider how much easier it is for a runner to reach full speed from a jog than from a standing start. 

Conduction of the action potential in myelinated axons is called saltatory conduction. Because ion flux only occurs at the nodes of Ranvier, the action potential jumps, in effect, from node to node. This provides two advantages, speeding the rate of conduction and reducing the metabolic cost of an action potential, because energy-dependent ion transporters are not needed along myelinated segments. 

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