III.

Tracing of Molecules and Atoms

Most substances are compounds consisting of molecules linked together in chemical combination or are mixtures of compounds. Only one type of molecule in a compound may be of importance in a particular tracer application. Important also, especially in biochemical research, is the ability to distinguish within a single compound similar molecules derived from two different sources. This information can be made available by the use of the technique called isotopic labeling.

Tracers are used in botanic and agricultural research to study the absorption of nutrients by plants and to trace metabolic pathways, especially those involved in photosynthesis.

In biological research, molecules labeled with radioactive isotopes have been especially useful in elucidating the metabolic pathways of biochemical synthesis and degradation. The routes of many nutrients and toxins through ecosystems have also been mapped by tracer techniques.

Tracer procedures are used in medical diagnosis and research to measure such functions of organs and tissues as their uptake of hormones, minerals, vitamins, blood or blood components, and drugs. Organ output of hormones or other proteins and wastes can also be measured with great speed and accuracy.