Energetics of -Oxidation

Palmitoyl-CoA yields 8 acetyl-CoA molecules and 14 pairs of hydrogen atoms, by seven cycles through the /6-oxidation system. Acetyl-CoA can be oxidized in the TCA cycle, used for the synthesis of fatty acid or cholesterol, or used for the formation of ketone bodies in liver. )6-Oxidation of an acyl-CoA with an uneven number of carbon atoms also yields a propionyl-CoA during the acetyl-CoA acyltransferase reaction of the last cycle. 

Two high-energy bonds are consumed in the activation of a fatty acid molecule. Every mole of fatty acyl-CoA that cycles through reactions 1-4 produces 1 mol of FADH2, 1 mol of NADH, and 1 mol of acetyl-CoA. On the last pass of an even-chain-length fatty acid, 2 mol of acetyl-CoA are formed and the final pass of an odd-chain-length molecule releases 1 mol of propionyl-CoA. The amount of ATP formed from complete oxidation of a hexanoic acid is calculated as shown in Table 18-2. 

Fatty acid oxidation produces more moles of ATP per mole of CO2 formed than does carbohydrate oxidation. In this case, oxidation of 1 mol of hexose produces at most (assuming malate shuttle operation exclusively) 38 mol of ATP. 

Complete oxidation of one molecule of palmitic acid yields 129 ATP molecules  

Each molecule of acetyl-CoA yields 12 ATP (12 x 8 = 96) FADH2 yields 2 ATP (7x2=14) NADH yields 3ATP (7x3 = 21) and two high-energy bonds are consumed (—2 ATP AMP PPj). Thus, net ATP production is 129. The energy yield from total combustion of palmitic acid in a bomb calorimeter (Chapter 5) is 

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Kinetics and Energetics of Oxidation of Bitumen in Relation to In Situ Combustion Processes... 

D. Alfe and M. J. Gillan, The Energetics of Oxide Surfaces by Quantum Monte Carlo, J. Phys. Condens. Matt. 18 (2006), F435. 

Energetics of oxidation-reduction (redox) reactions in solution are conveniently studied by arranging the system in an electrochemical cell. Charge transfer from the excited molecule to a solid is equivalent to an electrode reaction, namely a redox reaction of an excited molecule. Therefore, it should be possible to study them by electrochemical techniques. A redox reaction can proceed either by electron transfer from the excited molecule in solution to the solid, an anodic process, or by electron transfer from the solid to the excited molecule, a cathodic process. Such electrode reactions of the electronically excited system are difficult to observe with metal electrodes for two reasons firstly, energy transfer to metal may act as a quenching mechanism, and secondly, electron transfer in one direction is immediately compensated by a reverse transfer. By usihg semiconductors or insulators as electrodes, both these processes can be avoided. 

In evaluating the energetics of oxidizers, it is apparent that the perchlorate salts are more desirable than nitrate salts. Therefore one would expect that attempts would be made to incorporate the perchlorate group into binder structures. The study of perchlorate esters was not pursued when it was found that simple model compounds obtained from alcohols and perchloric acid were excessively shock sensitive. However, when the C104 group existed in ionic or salt-like form, these materials were found to be far less sensitive. Bell Aerosystems Corp., in conjunction with the Food Machinery Corp. prepared the polyethylene hydrazine perchlorates. 

SCHEME 11.21 Illustration of orbital shape and impact on energetics of oxidative addition and reductive elimination processes. Directed nature of carbon-based orbitals leads to reduced orbital overlap in the transition state relative to overlap of spherical hydrogen Is orbital. 

FIGURE 2, Energetics of Oxidation at the Semiconductor Electrolyte Interface. 

Isosafrol yields piperonal (heliotropine) melting at 37° as the principal product of oxidation when potassium permanganate is used as the oxidising agent. If the oxidation be very energetic piperonylic acid, melting at 228°, is the principal reaction product. 

Taken together, the overall reaction is simply the energetically favorable oxidation of hydrogen. 

Janssen PH, B Schink (1995a) Metabolic pathways and energetics of the acetone-oxidizing sulfate-reducing bacterium Desulfobacterium cetonicum. Arch Microbiol 163 188-194. 

Figure 18.6 Energetics of the ORR at the heme/Cu site of CcO the enzyme couples oxidation of ferroc3ftochrome c (standard potential about —250 mV all potentials are listed with respect to a normal hydrogen electrode) to reduction of O2 (standard potential at pH 7 800 mV). Of the 550 mV difference, only 100 mV is dissipated to drive the reaction 220 mV is expanded to translocate four protons from the basic matrix compartment to the acidic IMS (inter-membrane space). In addition 200 mV is converted into transmembrane electrostatic potential as ferroc3ftochrome is oxidized in the IMS, but the charge-compensating protons are taken from the matrix. The potentials are approximate.

Fig. 2 a Energetics of photo oxidation of G and A by singlet Sa. b Dynamics of charge separation (kcs) and charge recombination (kCY) for Sa-linked hairpins possessing a single guanine... 

Part 1. Kinetics and Energetics of Dry Oxidation. The simplest approach to data analysis is to assume that only a single class of oxidation reactions is important and to make the related assumption that the temperature dependence of the single rate constant k can be represented by an Arrhenius equation. In this way we obtain... 

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