Biochemical reactions electric potential

Possible driving forces for solute flux can be enumerated as a linear combination of gradient contributions [Eq. (20)] to solute potential across the membrane barrier (see Part I of this volume). These transbarrier gradients include chemical potential (concentration gradient-driven diffusion), hydrostatic potential (pressure gradient-driven convection), electrical potential (ion gradient-driven cotransport), osmotic potential (osmotic pressure-driven convection), and chemical potential modified by chemical or biochemical reaction. 

Of course, these reactions may be very much more complicated. Since the pH is specified, H + is not included as a reactant, and a reactant may be a sum of species if the reactant has pKs in the pH region of interest. These biochemical reactions do balance atoms of elements other than hydrogen, but they do not balance electric charges. When the half-reactions occur in half-cells connected by a KC1 salt bridge, the difference in electric potential between the metallic electrodes... 

Two attributes of synthetic membranes are often applied to the design of analytical devices as a selective barrier, and as a substrate in which chemical or biochemical reactions are performed. In many cases, the membrane helps translate the activity of specific analytes into easily measurable quantities such as electrical potentials or spectrophotomet-ric absorption. 

The process of information flow between neurons is termed synaptic transmission, and in its most basic form it is characterized by unidirectional communication from the presynaptic to postsynaptic neuron. The process begins with the initiation of an electrical impulse in the axon of the presynaptic neuron. This electrical signal—the action potential—propagates to the axon terminal, which thereby stimulates the fusion of a transmitter-fllled synaptic vesicle with the presynaptic terminal membrane. The process of synaptic vesicle fusion is highly regulated and involves numerous biochemical reactions it culminates in the release of chemical neurotransmitter into the synaptic cleft. The released neurotransmitter diffuses across the cleft and binds to and activates receptors on the postsynaptic site, which thereby completes the process of synaptic transmission. 

Biological macromolecules are often handled through microfluidic systems, in which these molecules can transport and react. A common driving force behind such microfluidic transport processes is the electrokinetic force, which originates as a consequence of interaction between the electric double-layer potential distribution and the applied electric field. This entry discusses some of the important features of the biochemical reactions in such microfiuidic systems. 

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