Regulatory mechanism, living cell

Living systems are complex, ordered systems. This complexity and order is reflected in the molecules characteristic of life, in their interactions with each other, in the regulatory mechanisms that result from these interactions, and in the complex supramolecular structures characteristic of cells. Organization is also reflected in ordered metabolic and signaling pathways. Such complex, ordered structures and pathways are not characteristic of inanimate objects. 

Evidence for a mechanism to exchange regulatory factors between the chromatin template and a nucleoplasmic compartment has been provided from imaging transcriptionally active chromatin loci in situ in live cells. Such studies have provided much information on the dynamics of histones and regulatory factors, as well as the large-scale organization of the loci in the context of the nuclear environment. 

Nobles M, Benians A, Tinker A (2005) Heterotrimeric G proteins precouple with G protein-coupled receptors in living cells. Proc Natl Acad Sci USA 102 18706-11 Ohara-Imaizumi M, Kameyama K, Kawae N et al (1992) Regulatory role of the GTP-binding protein, G(o), in the mechanism of exocytosis in adrenal chromaffin cells. J Neurochem... 

Finally, Section 2.4 analyses a simplified model of a bursting pancreatic /3-cell [12]. The purpose of this section is to underline the importance of complex nonlinear dynamic phenomena in biomedical systems. Living systems operate under far-from-equilibrium conditions. This implies that, contrary to the conventional assumption of homeostasis, many regulatory mechanisms are actually unstable and produce self-sustained oscillatory dynamics. The electrophysiological processes of the pancreatic /3-cell display (at least) two interacting oscillatory processes A fast process associated with the K+ dynamics and a much slower process associated with the Ca2+ dynamics. Together these two processes can explain the characteristic bursting dynamics in the membrane potential. 

Thus, further studies in the field of PolyP biochemistry offer great prospects, which will more than once give unexpected results for elucidating the most important regulatory mechanisms of the living cell. 

Any substance that reduces the velocity of an enzyme caialyzed reaction can be considered to be an "inhibitor. The inhibition of enzyme activity is one of the major regulatory devices of living cells, and one of the most important diagnostic procedures of the enzymologisL Inhibition studies often tell us something about the specificity of an enzyme, the physical and chemical architecture of the active site, and the kinetic mechanism of the reaction. In OUT everyday life, enzyme inhibitors can be found masquerading as drugs, antibiotics, preservatives, poisons, and toxins. In this section we examine a few simple types of enzyme inhibitors. 

The food that animals consume supplies their bodies with the nourishment required to sustain living processes. Complex regulatory mechanisms ensure that the demands of each cell for energy and... 

The ability of cofactors D and E to disrupt the tubulin heterodimer in vitro implies that overexpression of these cofactors in vivo might have a disruptive effect on the microtubule cytoskeleton. This expectation is borne out experimentally Cells overexpressing either of these cofactors lose most or all of their microtubules (Bhamidipati et al., 2000 Martin et al., 2000). It makes sense, therefore, that regulatory mechanisms should exist to ensure the balanced availability of these cofactors within living cells. Interaction of cofactors with native tubulin is also regulated by the small G protein Arl2 (Bhamidipati et al., 2000). 

Factors and conditions which influence the catalytic and kinetic characteristics of isolated enzymes are generally interpreted as regulatory mechanisms and are presumed to govern metabolic traffic in living cells— whether this is actually so is unproven. 

One can imagine, as Larsson and Reichard 22) have done, that the regulatory properties perceived through in vitro experiments, might operate in the living cell as a physiological mechanism which adjusts or balances production of the four deoxyribonucleotide building blocks needed for... 

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