Life's Potentials
93
number of electrons in place around each atom, the "extra" electrons of
the impurity atoms are free to move through the lattice without being
bound to any particular atom. If the impurity atoms have fewer electrons
than the others, the "holes" in their electron clouds can be filled by
electrons from other atoms, leaving holes elsewhere. A negative current,
or N-type semiconduction, amounts to the movement of excess elec-
trons; a positive current, or P-type semiconduction, is the movement of
these holes, which can be thought of as positive charges.
THREE WAYS OF CONDUCTING ELECTRICAL CURRENT
Szent-Gyorgyi pointed out that the molecular structure of many parts
of the cell was regular enough to support semiconduction. This idea was
almost completely ignored at the time. Even when Szent-Gyorgyi ex-
panded the concept in his
I960 Introduction to a Submolecular Biology,
most scientists (except in Russia!) dismissed it as evidence of his advanc-
ing age, but that little book was an inspiration to me. I think it may
turn out to be the man's most important contribution to science. In it
he conjectured that protein molecules, each having a sort of slot or way
station for mobile electrons, might be joined together in long chains so
that electrons could flow in a semiconducting current over long distances
without losing energy, much as in a game of checkers one counter could
jump along a row of other pieces across the entire board. Szent-Gyorgyi
suggested that the electron flow would be smilar to photosynthesis,
another process he helped elucidate, in which a kind of waterfall of elec-