ATP production and utilization

The ATP requirements to form one C-mole biomass is called the yield Tatp/x and the growth reaction reads  

ATP is required for growth and maintenance [55]. if maintenance is considered to be non growth-associated, the yield of ATP on biomass, corrected for maintenance, is calculated from the following relation [56,57,58]  

Maintenance is considered as ATP hydrolysis not coupled to another ender-gonic reaction. It is due to futile cycles, maintenance of gradients, and maintenance of metabolic machinery. 

The energetic cost of biomass formation can be estimated from biochemical data concerning the energetic cost of amino-acid synthesis and polymerization, as well as the cost to synthesize polysaccharides, RNA, DNA, lipids, etc. and 

The cost of biomass synthesis is easily determined in anaerobic cultures since oxidative phosphorylation is not active. The only ATP synthesis step is ethanol formation from pyruvate, and glycerol synthesis consumes one mole of ATP per mole formed. The ATP yield of anaerobic catabolic reactions is low as shown in Table 21. In fact, degradation of glucose is incomplete and the 

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This forms the basis of constructing an enthalpy budget in which the total enthalpy flux is compared with the scalar heat flux, 7q(W m-3), obtained from dividing heat flow by size (volume or mass) of the living matter. If account is made of all the reactions and side reactions in metabolism, the ratio of heat flux to enthalpy flux, the so-called energy recovery ( Yq/H = Jq/Jh) will equal 1. If it is more than 1, then the chemical analysis has failed fully to account for heat flux and if it is less than 1, then there are undetected endothermic reactions. Account for all reactions may seem a formidable task, but it should be borne in mind that anabolic processes dissipate insignificant amounts of heat compared with those of catabolism and that ATP production and utilization are balanced in cells at steady-state. Catabolism is generally limited to a relatively few well-known pathways with established overall molar enthalpies. So, as will be seen later, the task is by no means mission impossible. ... 

Under normal conditions, lactate is metabolized in the liver and the blood lactate level is between 1 and 2 mM. Lactate accumulation in body fluids can be due to increased production and/or decreased utilization. Blood lactate-to-pyruvate ratio below 25 suggests defects in a gluconeogenic enzyme (Chapter 15) or pyruvate dehydrogenase (discussed later). A common cause of lactic acidosis is tissue hypoxia caused by shock, cardiopulmonary arrest, and hypoperfusion. Inadequate blood flow leads to deprivation of oxygen and other nutrients to the tissue cells as well as to the removal of waste products. Oxygen deprivation leads to decreased ATP production and accumulation of NADH, which promotes conversion of pyruvate to lactate. 

Determination of CK activity CK catalyzes the reversible N-phosphorylation of creatine to form creatine phosphate by Mg -ATP/Mg -ADP complexes and thus is an important enzyme regulator of high-energy phosphate production and utilization within contractile tissues. CK occurs predominantly... 

Effects of Allelochemlcals on ATP Supply. Allelochemlcals might decrease the ATP content of tissue by either increasing ATP utilization or decreasing ATP production. Some allelochemlcals that inhibit mineral absorption decrease ATP content of plant tissues. Salicylic acid decreased the ATP content of oat roots in a pH dependent manner (Figure 3). This result suggested that mitochondrial production of ATP was decreased in the tissue. On the other hand, Tillberg (38) found that salicylic acid and cinnamic acid increased the ATP content of Scenedesmus. Various flavonoids inhibited ATP production by mitochondria Isolated from cucumber (Cucumls satlvus L.) hypocotyls (54). Flavones such as kaempferol were more inhibitory than the corresponding flavanones. Substituted cinnamic acids such as caffeic acid were not inhibitory. 

The amino group now provides the nucleus for purine ring formation, an extended series of reactions we shall not describe. The first-formed purine product is inosine 5 -phosphate (IMP), which leads to either AMP or GMP these require amination at alternative sites, and utilize either GTP- or ATP-dependent reactions for amination. GTP or ATP (as appropriate) will also be required for further phosphorylations to produce the nucleotide triphosphates. 

The equilibrium constant of an enzyme-catalyzed reaction can depend greatly on reaction conditions. Because most substrates, products, and effectors are ionic species, the concentration and activity of each species is usually pH-dependent. This is particularly true for nucleotide-dependent enzymes which utilize substrates having pi a values near the pH value of the reaction. For example, both ATP" and HATP may be the nucleotide substrate for a phosphotransferase, albeit with different values. Thus, the equilibrium constant with ATP may be significantly different than that of HATP . In addition, most phosphotransferases do not utilize free nucleotides as the substrate but use the metal ion complexes. Both ATP" and HATP have different stability constants for Mg +. If the buffer (or any other constituent of the reaction mixture) also binds the metal ion, the buffer (or that other constituent) can also alter the observed equilibrium constant . ... 

Salicylic acid, the major metabolite of aspirin, uncouples the electron transport chain in the mitochondria. This results in (a) increased use of oxygen and production of carbon dioxide, (b) lack of ATP, and (c) excess energy no longer utilized in ATP production. The result is increased respiration and raised temperature. The alterations in respiration lead to alkalosis followed by acidosis. The lack of ATP and loss of respiratory control will cause increased metabolic activity and hypoglycemia after an initial mobilization of glucose from glycogen. 

The energy must be in A/ZII form, equivalent to Ai//and ApH. The mitochondrial reaction mechanism (3.54) involving H+-ATP-synthase is illustrated [22] in Figure 3.3a. The advantage of this scheme is that it indicates ways of consumption of substrates and products in A/ZII generation and utilization, i.e. protons transported by means of the F0 factor to the water molecule are included, produced in the reaction (3.54). 

Figure 2.13. Upper panel is a summary diagram of the standard model of metabolic regulation in this conceptualization, accelerating tissue ATP utilization leads to increasing concentrations of ADP and Pi, which serve as substrates for oxidative phosphorylation, to activate ATP production. Lower panel summarizes an alternate model of metabolic regulation in which ATP demand and ATP supply pathways are simultaneously activated during large-scale change in tissue work rates. See text for further details.

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