Which medium is used for size-based separation in electrophoresis?

• A. Agarose
• B. Cellulose acetate
• C. PAGE
• D. Polyacrylamide

Answer: (B)

Size-based separation in electrophoresis relies on the medium acting as a physical sieve. A cellulose acetate membrane has a relatively uniform, fixed pore size, so when an electric field drives molecules through it, smaller molecules pass through the pores more easily while larger ones are hindered. This differential ability to traverse the membrane's pores causes molecules to separate according to their size. While other media like agarose and polyacrylamide also separate by size due to their gel networks, cellulose acetate provides a straightforward size discrimination because of its membrane-based structure.