[2]Metabolism is the sum of the life-sustaining activities in a living organism, including nutrition, production of energy, and synthesis (building) of new living material.

[3]Morphologists are biologists specializing in the structure of organisms or in the study of whole organisms. Biochemists, by contrast, study chemical reactions of biological materials.

[4]This is not to be confused with a cell nucleus. This word was borrowed from biology for atomic theory, however.

[5]An exception is the hydrogen atom, which has no neutron in its nucleus.

[6]Mev is the abbreviation for million electron volts.

[7]A concept for which James D. Watson of the United States and Francis H. C. Crick of England shared a Nobel Prize in 1962.

[8]The study of tissues.

[9]There are additional, more subtle metabolic events that lead to the synthesis of DNA, but they are not important in this discussion.

PHOTO CREDITS

[Figure 1] Armed Forces Institute of Pathology Negative No. 4156 [Figure 3] Dr. T. Tahmisian, Argonne National Laboratory [Figure 4] Oak Ridge National Laboratory (photo on right) [Figure 5] Oscar W. Richards, American Optical Company [Figure 7] Brookhaven National Laboratory [Figure 9] Battelle-Northwest Laboratory [Figure 10] Oak Ridge National Laboratory [Figure 19] Argonne National Laboratory [Figure 23] Argonne National Laboratory [Figure 24] Argonne National Laboratory [Figure 28] Argonne National Laboratory [Figure 29] Brookhaven National Laboratory