Integrated SequencePhysics Chemistry Organic Biology

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Chem1 Virtual Textbook - Galvanic cells and electrodes
Outstanding tutorial on galvanic cells.

Purdue University - Electrical Work From Spontaneous Oxidation-Reduction Reactions
Comprehensive tutorial. Very well done.

Chem1 Virtual Textbook - Electrochemical energy storage and conversion
Good review of some of the principles of electrochemistry in this discussion of various batteries and fuel cells.

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Special points of emphasis

Chemical Thermodynamics and the Equilibrium State



DC Current

In an electrolytic cell, the voltage placed across the electrodes causes an otherwise nonspontaneous reaction to occur. A galvanic cell, however, contains the components of a spontaneous chemical reaction, with the oxidation and reduction half-reactions occurring in separate compartments of the cell. The free energy of reaction is liberated to drive an electron flow outside the cell. Whether the cell is electrolytic or galvanic, the electrode where oxidation occurs is called the anode, and the electrode where reduction occurs is called the cathode. In an electrolytic cell, though, oxidation at the anode must be forced to occur by the application of positive potential, and likewise the cathode in an electrolytic cell is negative. In a galvanic cell, on the contrary, oxidation is occurring spontaneously, feeding electrons to the circuit, so the anode is negative, and the cathode is positive, where cations are waiting to be reduced. The voltage difference, or emf, between the poles of a galvanic cell is called its cell potential, Ecell.

The Eukaryotic Cell



Bioenergetics and Cellular Respiration

The matrix and intermembraneous space of mitochondria can be conceptualized as the two half-cells of a galvanic cell. The positive cell potential of such a galvanic cell represents the free energy available for the oxidation of NADH or FADH2 by O2. The 'load' of the cell involves pumping protons from the matrix into the intermembraneous space, converting the energy expended by the above reaction into an electropotential and diffusion gradient involving differences in H+ concentration across the inner mitochondrial membrane. The free energy of this H+ concentration gradient is ultimately used to carry out ATP generation.

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