Final answer:
The statement is true; isolated cellular fractions after cell fractionation can contain impurities due to the presence of organelles with similar masses, and further confirmation and purification steps may be required.
Step-by-step explanation:
The statement that isolated fractions are not always pure and may contain contamination of smaller organelles or particles is true. When cell fractionation is performed, the goal is to separate cells into their constituent parts, including organelles like mitochondria, chloroplasts, and nuclei. However, due to the similarity in mass and size of various organelles, some contamination may occur. After initial fractionation, scientists use techniques such as electron microscopy and biochemical tests to further confirm the identity of the isolated structures. It is important to carry out additional purification steps if highly pure samples are required for downstream applications.