Cell metabolism coordination

Chen MH, Liu LF, Chen YR, Wu HK, Yu SM (1994) Expression of a-amylases, carbohydrate-metabolism, and autophagy in cultured rice cells is coordinately regulated by sugar nutrient. Plant J 6 625—636. 

Figure 2 Schematic of the transport of metal associated with particles and fibers by the host Mediators can function to protect the host by (1) directing an influx of inflammatory cells that have a capacity to isolate the iron by reducing the Fe " using superoxide and (2) modifying iron metabolism in the host resulting in the sequestration of the catalytically active iron associated with these dusts. Mediator release after exposure to silica and asbestos may represent an attempt of the cell to coordinate the transport and sequestration of catalytically active iron. This response would diminish the oxidative stress associated with the particle and fiber and injury after their exposure.

In summary, the capacity to synthesize both hemoproteins and iron sulfur proteins appears to be a ubiquitous attribute in organisms attacking reduced inorganic substrates. If the reactions by which these cells obtain energy represent relics of ancient forms of metabolism, it can only be concluded that heme formation and iron-sulfur coordination must have been invented at a very early stage in evolution. 

No carrier is completely specific for a given trace metal metals of similar ionic radii and coordination geometry are also susceptible to being adsorbed at the same site. The binding of a competing metal to an uptake site will inhibit adsorption as a function of the respective concentrations and equilibrium constants (or kinetic rate constants, see below) of the metals. Indeed, this is one of the possible mechanisms by which toxic trace metals may enter cells using transport systems meant for nutrient metals. The reduced flux of a nutrient metal or the displacement of a nutrient metal from a metabolic site can often explain biological effects [92]. 

Ethylene coordinates the expression of genes responsible for enhanced respiratory metabolism, chlorophyll degradation, carotenoid synthesis, conversion of starch to sugars, increased activity of cell wall-degrading enzymes, aroma volatile production, and so on. All these events stimulate a series of biochemical, physiological, and structural changes making fruits mature and attractive to the consumer. 

Enzymes are biological catalysts—i. e substances of biological origin that accelerate chemical reactions (see p. 24). The orderly course of metabolic processes is only possible because each cell is equipped with its own genetically determined set of enzymes. It is only this that allows coordinated sequences of reactions (metabolic pathways see p. 112). Enzymes are also involved in many regulatory mechanisms that allow the metabolism to adapt to changing conditions (see p.ll4). Almost all enzymes are proteins. However, there are also catalytically active ribonucleic acids, the ribozymes" (see pp. 246, 252). 

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