Cell movement

thumb|280px|3D rendering of centrioles showing the triplets

A flagellum (; : flagella) (Latin for 'whip' or 'scourge') is a hair-like appendage that protrudes from certain plant and animal sperm cells, from fungal spores (zoospores), and from a wide range of microorganisms to provide motility. Many protists with flagella are known as flagellates.

The cilium (: cilia; ; in Medieval Latin and in anatomy, cilium) is a short hair-like membrane protrusion from many types of eukaryotic cell. (Cilia are absent in bacteria and archaea.) The cilium has the shape of a slender threadlike projection that extends from the surface of the much larger cell body. Eukaryotic flagella found on sperm cells and many protozoans have a similar structure to motile cilia that enables swimming through liquids, but they are longer than cilia and have a different undulating motion.

thumb|Amoeba proteus extending lobose pseudopodia|300x300px

A sarcomere (Greek σάρξ sarx "flesh", μέρος meros "part") is the smallest functional unit of striated muscle tissue. It is the repeating unit between two Z-lines. Skeletal muscles are composed of tubular muscle cells (called muscle fibers or myofibers) which are formed during embryonic myogenesis. Muscle fibers contain numerous tubular myofibrils. Myofibrils are composed of repeating sections of sarcomeres, which appear under the microscope as alternating dark and light bands. Sarcomeres are composed of long, fibrous proteins as filaments that slide past each other when a muscle contracts or r

biological molecular machines

thumb|Cytokinesis|Cell division. All cells can be considered motile for having the ability to divide into two new daughter cells.

class of molecular motors

controlled self-propelled movement of a cell from one site to a destination guided by molecular cues

Most common mode of locomotion in eukaryotic cells

Myofilaments are the three protein filaments of myofibrils in muscle cells. The main proteins involved are myosin, actin, and titin. Myosin and actin are the contractile proteins and titin is an elastic protein. The myofilaments act together in muscle contraction, and in order of size are a thick one of mostly myosin, a thin one of mostly actin, and a very thin one of mostly titin.

180px|thumb|This electron micrograph shows exaggerated filopodia with club-like shape induced by formin mDia2 in cultured cells. These filopodia are filled with bundled microfilament|actin filaments which were born in and converged from the lamellipodial network.

The lamellipodium (: lamellipodia) (from Latin lamella, related to '', "thin sheet", and the Greek radical pod-'', "foot") is a cytoskeletal protein actin projection on the leading edge of the cell. It contains a quasi-two-dimensional actin mesh; the whole structure propels the cell across a substrate. Within the lamellipodia are ribs of actin called microspikes, which, when they spread beyond the lamellipodium frontier, are called filopodia. The lamellipodium is born of actin nucleation in the plasma membrane of the cell and is the primary area of actin incorporation or microfilament formatio

An undulipodium or undulopodium (Greek: "swinging foot"; plural undulipodia) is a motile filamentous extension of eukaryotic cells, composed of a membrane protrusion held by a cytoskeletal structure called the axoneme. It is divided into cilia and flagella – which are differing terms for structurally identical organelles used on different types of cells, but are distinguished according to function and/or length, and usually corresponds to different waveforms of the organelles beating motion. The Gene Ontology database does not make a distinction between the two, referring to most undulipodia a

small region on the surface of a cell that anchors the cell to the extracellular matrix and that forms a point of termination of actin filaments

Explanation of muscle contraction

bulge in the plasma membrane of a cell

protein structure in cilia and flagella