ABSTRACT
In Chapter 1 , it was mentioned that or free energy, can be thought of as coherent or directed motion. On this basis , a gradient of molecules diffusing from to low concentration can be made to do work move a for example) . To create a gradient requires work (we need to push back on thepistontoconcentratethemoleculesintoasmaller volume) .Similarly,tocreateaconcentrationgradientacross abiologicalmembranerequireswork.Thiscanbeprovided bycouplingthevectorialmovementtoothermorefavourable changes such as a redox reaction or the hydrolysis of ATP. Discharging the gradient releases the stored free energy, which in turn may be coupled to reactions.
