No. They are polymers of actin that form 'filaments'. Membranes in eukaryotic cells are composed of a 'lipid bilayer'
Actin and myosin
Actin Filaments
Actin is a contractile protein fibers present in muscles.It occurs in two forms a.monomeric G actin b. polymeric F ACTIN.
Actin was discovered by Straub in 1942.
Actin is a globular molecule
Actin
Actin Changes ShapeApexMyosin binds to ActinAPEX
Assuming you meant microfilament, it is mostly comprised of linear polymers of actin, or actin filaments. Some use "actin filament" (or sometimes just "actin") and "microfilament" interchangably.
Actin is thin, pulled together by myosin.
Actin
Actin Changes ShapeApexMyosin binds to ActinAPEX