Bioelectrochemistry
Overall chemical reactions take place through a series of electron transfers between molecules. The electrons are
transferred between active sites of molecules. The active sites typically contain redox active inorganic ions at which
electrons can be accepted/donated.
There are 4 main types of half cells:
A metal ion in a solution of its ions.
A gas in contact with a solution of its ions.
Two different oxidation states of the same soluble species.
Metal in contact with an insoluble salt.
The electrode potential system used for biological systems is usually two different oxidation states of the same soluble
species in contact with an electrode. The cell voltage should be measured in standard conditions with all species in a
1M concentration and all pressures of gases at 1 atm. All substances should be pure, electrodes inert in Pt and a
temperature of 298K. The measured electrode voltage is then; E cell = E right - E left E cell= E reduced - E oxidised.
Free Energy Relationship; ΔGθ = -n x F x E cell. n is the number of electrons transferred in the half cell reactions and
F is Faraday’s constant. When E cell is positive Gibbs is negative and the reaction is spontaneous. When E cell is
negative, Gibbs is positive and the reverse reaction is spontaneous.
Standard state is 1M, but most biological systems cannot survive in this state. The biochemical standard state has the
same definition except [H+] = 1x10-7M pH = 7.
Bioelectrochemistry 1
Overall chemical reactions take place through a series of electron transfers between molecules. The electrons are
transferred between active sites of molecules. The active sites typically contain redox active inorganic ions at which
electrons can be accepted/donated.
There are 4 main types of half cells:
A metal ion in a solution of its ions.
A gas in contact with a solution of its ions.
Two different oxidation states of the same soluble species.
Metal in contact with an insoluble salt.
The electrode potential system used for biological systems is usually two different oxidation states of the same soluble
species in contact with an electrode. The cell voltage should be measured in standard conditions with all species in a
1M concentration and all pressures of gases at 1 atm. All substances should be pure, electrodes inert in Pt and a
temperature of 298K. The measured electrode voltage is then; E cell = E right - E left E cell= E reduced - E oxidised.
Free Energy Relationship; ΔGθ = -n x F x E cell. n is the number of electrons transferred in the half cell reactions and
F is Faraday’s constant. When E cell is positive Gibbs is negative and the reaction is spontaneous. When E cell is
negative, Gibbs is positive and the reverse reaction is spontaneous.
Standard state is 1M, but most biological systems cannot survive in this state. The biochemical standard state has the
same definition except [H+] = 1x10-7M pH = 7.
Bioelectrochemistry 1
