Biochemical reactions spontaneity

Table 2 illustrates the effect of the Gibbs free energy on the spontaneity of a chemical/biochemical reaction and the resulting release of energy. Thus, it is useful to use AG values for any biochemical reaction mediated by microbes to determine whether energy is liberated for work, and how much energy is liberated. 

The thermodynamic principles described in Chapter 2 of this volume can be used to indicate whether or not a reaction can take place spontaneously. They do not, however, provide information about the rate at which a reaction will proceed. Most biochemical reactions proceed so slowly at physiological temperatures that catalysis is essential for the reactions to proceed at a satisfactory rate in the cell. 

Reactions in living organisms are no different from reactions in laboratory flasks. Both follow the same laws, and both have the same kinds of energy requirements. For any biochemical reaction to occur spontaneously, AG must be negative. For example, oxidation of 1 mol of glucose, the principal source of energy for animals, has AG° = —2870 kj. 

When the pH is specified, the criterion for spontaneous change and equilibrium is provided by the transformed Gibbs energy and the reactants can be taken to be HgvM, HgvMOa, and O2 that are involved in the following biochemical reaction. 

The human body is a remarkably efficient organism that is able to reduce the amount of waste and ensure that energy liberated in one part of a biochemical reaction is actually used up, or stored, in another part of such a reaction. This means that we exist more or less at steady state giving out very little surplus energy. In fact, the amount of heat that we lose is equivalent to less than that of an electric light bulb. Less efficient organisms lose a great deal of heat and, hence, one sees spontaneous combustion of farmers haystacks because of bacterial inefficiency en masse. 

Recall from Chapter 4 that the principles of thermodynamics can predict whether a reaction is spontaneous. However, thermodynamic quantities do not provide any information regarding reaction rates. To be useful to an organism, biochemical reactions must occur at reasonable rates. The rate or velocity of a biochemical reaction is defined as the change in the concentration of a reactant or product per unit time. The initial velocity v0 of the reaction A —> P where A = substrate and P = product is... 

Regardless of the AG" for a particular biochemical reaction, it will proceed spontaneously within cells only if AG is negative, given the usual intracellular concentrations of reactants and products. For example, the conversion of glyceraldehyde 3-phosphate (G3P) to dihydroxyacetone phosphate (DHAP), two Intermediates in the breakdown of glucose,... 

Thermodynamics of a biochemical reaction refers to whether a reaction is spontaneous. A spontaneous reaction has a negative Gibbs free energy or AG°. 

The reaction is spontaneous, as indicated by the AG°. However, remember that even though this reaction is spontaneous, nothing would happen if you simply put these chemicals in a test tube. Biochemical reactions require enzymes to catalyze them. 

Example ATP/ADT/AMP reactions are exothermic and exergonic these provide the energy and driving force to complete less spontaneous biochemical reactions Example ATP + HjO => ADP + energy... 

The major source of energy for microorganisms of the detrital chain, for their sustenance and multiplication, is spontaneous redox reactions. The role of microorganisms is only in lowering their activation energy through a number of additional biochemical reactions, which transfer electrons from the donor to the acceptor minimum energy expenses. The acceptor... 

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