CELLULAR BIOLOGYLECTUREUniversity of Science and Technology HanoiLecturer: Thao Thi Do PhD.Laboratory for BioassayINSTITUTE OF BIOTECHNOLOGYVIETNAM ACADEMY OF SCIENCE AND TECHNOLOGY
Cell MovementCell movement:•Internal: cytoplasmic streaming•External: motility.Internal movements (organelles): by actin filamentsand other components of the cytoskeleton.Thecytoskeleton:networkoffilamentsandtubules; extends from the nucleus to the plasmamembrane.
Internal Cell MovementActin filaments: long, thin, polar fibers (7 nm in diameter).An actin filament: consists of two chains of globular actinmonomers twisted to form a helix.Actin filaments of intestinal cells act to shorten the celland thus to pull it out of the intestinal lumen.In plant cells, actin filaments form tracts along whichchloroplasts circulate.
Internal Cell MovementActinfilamentsmovebyinteractingwithmyosin. (Myosins: a family of ATP-dependentmotorproteins).Motorproteins:areaclassofmolecularmotors; powered by the hydrolysis ofATP; convertchemical energy into mechanical work
•Intermediate filaments: 8-11nmindiameter.•Theintermediatefibers:rope-likeassemblies of fibrous polypeptides.•Support the nuclearenvelope,plasmamembrane,formcell-to-celljunctions.
Cellscanmovebyspecializedstructures:ciliaorflagella•Cilia: tiny hairs along the outside membrane;push the cell along•Flagella: much larger hairs, propel cell backExternal Cell Movementand forth.•Bothciliaandflagella:composedofmicrotubules.
External Cell Movement•Cilia:short,numerous,hairlikeprojections(move in an undulating fashion)•Flagella: longer, fewer in number, projectionsthat move in whip-like fashion (sperm cells).°Cilia and flagella move: microtubules slide past oneanother, structures same arrangement as centrioles.°Flagella works as whips pulling (Chlamydomonas)or pushing(dinoflagellates) the organism throughthe water.