Isotopic labeling of a specific substrate carbon with 13C, which has an extra neutron, is particularly useful for investigating biochemical pathways because:

a. the radioisotope blocks each pathway at a specific step.
b. radiolabels generally are easier to track in cells than fluorescent labels.
c. the radioisotope readily exchanges neutrons so that all neighboring carbons become labeled and easier to detect with NMR.
d. the position of the labeled carbon can be traced through products of the pathway to characterize the pathway reactions.
e. the presence of the radioisotope greatly accelerates the pathway, which makes it easier to study.

Explanation:

Isotopic labeling is a  type of technique that has an important role in the identification or detection of the pathway during the reaction or in the cell. In this technique, the reactant is labeled and the labelled reactant is used in the reaction. When C13 is used to identify the pathway, the labeled carbon is easily identified in the products and thus the pathway of the reaction can be detected.

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these is a strong electrostatic attraction between the ions hence a lot of energy is needed to overcome this attraction

this is why the boiling points are so high