What method separates macromolecules by size and charge?

• A. Chromatography
• B. Mass spectrometry
• C. Gel electrophoresis
• D. Spectrophotometry

Answer: (C)

Separating macromolecules by size and charge relies on how a gel matrix and an electric field interact with molecules. The gel acts like a sieve: as the electric field pulls molecules through the mesh, smaller molecules weave through the pores more easily and move faster, while larger ones are slowed. At the same time, the net charge of a molecule determines how strongly it is pulled toward the opposite electrode, so more highly charged molecules migrate faster. Together, these factors cause distinct bands to form for molecules of different sizes and charges. Gel electrophoresis is the technique that uses this setup to resolve proteins and nucleic acids by size (and charge effects). Other methods like chromatography, mass spectrometry, or spectrophotometry don’t produce this gel-based size-and-charge separation in the same way.