In flow cytometry, what does side scatter help measure?

In flow cytometry, side scatter is primarily utilized to assess cell complexity and granularity. This measurement arises from the interaction of light with cellular structures and is influenced by both the internal structures of the cells, such as organelles, and the presence of granules within the cytoplasm.

Cells with a higher degree of granularity, such as granulocytes, will scatter light differently than more uniform or less granular cells, like lymphocytes. This parameter, in combination with forward scatter—which measures cell size—allows for a more detailed characterization of the cellular population. Hence, the relevance of side scatter as it pertains to assessing complexity and granularity within cells makes the choice correct for this question.

The other options pertain to different measurements: cell size is specifically assessed via forward scatter, cell surface markers are evaluated using fluorescence from labeled antibodies, and cell membrane potential typically requires additional methodologies not assessed through light scattering alone. This clear distinction underscores why side scatter is specifically linked to complexity and granularity.