biology-dictionary_11-06-2009

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Electric potential
The difference in the amount of electric charge between a region of positive charge and a
region of negative charge. The establishment of electric potentials across the plasma
membrane and across organelle membranes makes possible a number of phenomena,
including the chemiosmotic synthesis of ATP, the conduction of nerve impulses, and muscle
contraction.
Electrochemical gradient
The diffusion gradient of an ion, representing a type of potential energy that accounts for
both the concentration difference of the ion across a membrane and its tendency to move
relative to the membrane potential.
Electrogenic pump
An ion transport protein generating voltage across the membrane.
Electromagnetic spectrum
The entire spectrum of radiation; ranges in wavelength from less than a nanometer to more
than a kilometer.
Electron
A particle with a single negative charge; one or more electrons orbit the nucleus of the
atom.
Electron acceptor
Substance that accepts or receives electrons in an oxidation-reduction reaction, becoming
reduced in the process.
Electron carrier
A molecule that conveys electrons; one of several membrane proteins in electron transport
chains in cells. Electron carriers shuttle electrons during the redox reactions that release
energy used to make ATP.
Electron donor
Substance that donates or gives up electrons in an oxidation-reduction reaction, becoming
oxidized in the process.

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