Intermediate filaments (IFs) are rope-like protein fibers that form part of the cytoskeleton in eukaryotic cells. They are called “intermediate” because their diameter (~10 nm) is between that of microfilaments (~7 nm) and microtubules (~25 nm). Unlike the other cytoskeletal elements, intermediate filaments are not involved in motility but instead provide mechanical strength and structural stability to cells.
Structure:
Composed of fibrous proteins (not globular like actin or tubulin).
These proteins form coiled-coil dimers, which assemble into tetramers, then into protofilaments, and finally into a strong, rope-like filament.
Non-polar: Unlike microtubules and microfilaments, intermediate filaments lack polarity, so they don’t serve as tracks for motor proteins.
Functions:
Function
Description
Mechanical strength
Help cells withstand mechanical stress (e.g., stretching, pressure)
