Short /Long answer type question.
How the tracer technique is useful in determining the reaction sequence of the metabolic process? Explain with the help of Calvin cycle.

In the radioactive tracer technique, radioactive nucleotides are used to follow the behavior of elements or chemical species in chemical and other processes. In 1913, Hevesy and Paneth succeeded in determining the extremely low solubility of lead salts by using naturally occurring 210Pb as a radioactive tracer. Now many artificially radioactive tracer elements are available.

In 1946 Calvin began his work on photosynthesis.

After adding carbon dioxide with trace amounts of radioactive carbon-14 to an illuminated suspension of the single-cell green alga Chlorella pyrenoidosa, he stopped the alga’s growth at different stages and used paper chromatography to isolate and identify the minute quantities of radioactive compounds. This enabled him to identify most of the chemical reactions in the intermediate steps of photosynthesis—the process in which carbon dioxide is converted into carbohydrates. This was the first use of a carbon-14 tracer to explain a chemical pathway.

The Calvin cycle (also known as the Benson-Calvin cycle) is the set of chemical reactions that take place in chloroplasts during photosynthesis.
The cycle is light-independent because it takes place after the energy has been captured from sunlight.
The steps in the cycle are as follows:
1. Grab: A five-carbon carbon catcher called RuBP (Ribulose bisphosphate) catches one molecule of carbon dioxide and forms a six-carbon molecule.
2. Split: the enzyme RuBisCO (with the energy of ATP and NADPH molecules) breaks the six-carbon molecule into two equal parts.
3. Leave: A trio of carbons leave and become sugar. The other trio moves on to the next step.
4. Switch: Using ATP and NADPH, the three carbon molecule is changed into a five-carbon molecule.

5. The cycle starts over again.