Free energy enzymes affecting

Entropy A measure of the amount of disorder in a substance or system. Entropy is usually measured in joules/mole degree Kelvin or calories/mole degree Kelvin (compare with enthalpy and Gibbs free energy). Enzyme A biomolecule that catalyzes a change in another molecule without being affected itself. 

Some of the principles of thermodynamics were introduced in Chapter 1 —notably the idea offree energy (G). To fully understand how enzymes operate, we need to consider two thermodynamic properties of the reaction (1) the free-energy difference (A G) between the products and reactants and (2) the energy required to initiate the conversion of reactants to products. The former determines whether the reaction will be spontaneous, whereas the later determines the rate of the reaction. Enzymes affect only the latter. First, we will consider the thermodynamics of reactions and then, in Section 8.3. the rates of reactions. 

Enzymes derive both their selectivities and their reaction rate enhancements by the formation of enzyme-substrate complexes. This complex formation results in a transition state for the reaction, that lowers AG, the activation energy, but does not affect the net free energy for the conversion of substrate to product. This finding is represented in Figure 2.5, for the simple one-substrate enzyme reaction shown in Eq. 2.10 ... 

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