Which term describes the movement of suspended particles through a fluid or gel under the influence of an electric field?

• A. Electrophoresis
• B. Dialysis
• C. Gel filtration
• D. Chromatography

Answer: (A)

Electrophoresis is the movement of suspended particles through a fluid or gel under an applied electric field. Charged particles migrate toward the electrode with the opposite charge, and their speed depends on how strongly they are charged, their size and shape, and the medium’s properties. In a gel, the network acts like a sieve: smaller or more highly charged particles navigate the pores more easily, allowing separation by size and charge. For example, DNA fragments all carry negative charges and move toward the positive electrode, with smaller fragments traveling faster and separating over time.

Dialysis relies on diffusion across a semipermeable membrane driven by concentration differences, not an electric field. Gel filtration (size-exclusion chromatography) separates mainly by size using porous beads. Chromatography broadly encompasses separation by interactions with a stationary phase and mobile phase, which may or may not involve an electric field.