Biochemical balances, maintainance

Your body is constantly striving for a healthy biochemical balance as well. It tries to maintain homeostasis through many different means, including breathing, blood circulation, digestion, and hormone production. In addition to these basic life functions, the body has intrinsic ways of restoring pH balance when it is shifting too far to the acid side of the spectrum it excretes toxic acids from the blood via the kidneys, and it dumps alkaline minerals from other locations in the body into the blood to neutralize the acidity. 

Thus both renal and pulmonary activity are involved in maintaining the pH of blood at its normal level and their cooperative effects are typical of the many biochemically balanced systems which are dynamically integrated within organisms. 

Trace elements are essential cofactors for numerous biochemical processes. Trace elements that are added routinely to PN include zinc, selenium, copper, manganese, and chromium. There are various commercial parenteral trace element formulations that can be added to PN admixtures (e.g., MTE-5 ). Zinc is important for wound healing, and patients with high-output fistulas, diarrhea, burns, and large open wounds may require additional zinc supplementation. Patients may lose as much as 12 to 17 mg zinc per liter of gastrointestinal (GI) output (e.g., from diarrhea or enterocutaneous fistula losses) however, others have demonstrated that 12 mg/day may be adequate to maintain these patients in positive zinc balance.18 Patients with chronic diarrhea, malabsorption, and short-gut syndrome may have increased selenium losses and may require additional selenium supplementation. Patients with severe cholestasis should have copper and manganese... 

Body temperature is maintained by the balance between heat production and heat loss. Heat is produced in aU biochemical... 

Metabolic fluxes are responsible for maintaining the homeostatic state of the cell. This condition may be translated into the assumption that the metabolic network functions in or near a non-equilibrium steady state (NESS). That is, all of the concentrations are treated as constant in time. Under this assumption, the biochemical fluxes are balanced to maintain constant concentrations of all internal metabolic species. If the stoichiometry of a system made up of M species and N fluxes is known, then the stoichiometric numbers can be systematically tabulated in a... 

In the natural cycles of elements and molecules, the biochemical and chemical transformations have been recycling the elemental compounds for millennia, maintaining a balance and a cycling rate that allows natural ecosystems and organisms to coexist. Originally, the concept of Environmental Chemistry focused on... 

Plants that are acclimated and adapted to dry conditions reduce their photosynthetic capacity and leaf nitrogen content toward a level that matches the low stomatal conductance that is necessary to conserve water in these environments (Wright et al., 2001). A high photosynthetic capacity provides little benefit if the plant must maintain a low stomatal conductance to conserve water. Conversely, low nitrogen availability or other factors that constrain leaf nitrogen concentration result in leaves with low stomatal conductance. This strong correlation between photosynthetic capacity and stomatal conductance maintains the balance between photosynthetic capacity and CO2 supply, i.e., the cohmitation of photosynthesis by dififusional and biochemical processes. In addition to their low photosynthetic capacity and low stomatal conductance, plants in... 

In a linear chemical reaction system, there is a unique steady state determined by the chemical constraints that establish the NESS. For nonlinear reactions, however, there can be multiple steady states [6]. A network comprised of many nonlinear reactions can have many steady states consistent with a given set of chemical constraints. This fact leads to the suggestion that a specific stable cellular phenotypic state can result from a specific NESS in which the steady operation of metabolic reactions maintains a balance of cellular components and products with the expenditure of biochemical energy [4]. Similarly, the network of chemical and mechanical signals that regulate the metabolic network must also be in a steady state. Important problems, then, are to determine the variety of steady states available to a system under a given set of chemical constraints and the mechanisms by which cells undergo... 

The second Half of this chapter concerns material of a less biochemical and a more nutritional nature. Three types of proteiir nutrition are illustrated by studies with humans (1) the total fast, (2) the carbohydrate-only fast, and (3) a diet intended to maintain nitrogen balance. 

The nutrient balance technique is sometimes used to determine requirements, as illustrated by the example of growing monkeys in the Protein chapter. This intake indicates only the amount required to maintain a constant level of the nutrient in the body. Under some conditions, the determination of the minimal intake that can support nutrient balance in an adult animal does not necessarily indicate the requirement (Mertz, 1987). Other techniques must then be used to detennine if higher, but still constant, levels are of greater value to the animal. Here, biochemical tests may be used to assess a relevant physiological function. Kopple (1987) has pointed Out a number of difficulties in using the nutrient balance technique. For example, the value for nutrient intake tends to be overestimated and that for excretion tends to be underestimated. These two factors car> lead to an artifactually high value for the nutrient balance. 

Minerals dissolved in the body fluids are responsible for nerve impulses and the contraction of muscles, as well as for water- and acid-base balance. They play an important role in maintaining the respiration, heart rate, and blood pressure in normal limits. Deficiency of minerals in the diet may lead to severe, chronic clinical signs of diseases, frequently reversible after their supplementation in the diet, or following the total parenteral nutrition. Their influence on biochemical reactions in living systems also makes it possible to use them intentionally in many food processes. 

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