Cell movement or motility is a highly dynamic phenomenon that is essential to a variety of biological processes such as the development of an organism (morphogenesis), wound healing, cancer metastasis and immune response.

The processes that determine molecular movement across membranes are diffusion, pinocytosis, carrier-mediated transport and transcellular transport [5]. The types of carrier-mediated transport are described in Chapter 5.

Six Different Types of Movement Across Cell Membrane

• Simple Diffusion.
• Facilitated Diffusion.
• Osmosis.
• Active Transport.
• Endocytosis.
• Exocytosis.

 There are three main kinds of passive transport – Diffusion, Osmosis and Facilitated Diffusion.

Cell locomotion depends on two principal types of movement: the ciliary or flagellar movement and the amoeboid movement.

The cytoskeleton is the component of the cell that makes cell movement possible. This network of fibers is spread throughout the cell’s cytoplasm and holds organelles in their proper place. Cytoskeleton fibers also move cells from one location to another in a fashion that resembles crawling.

Filopodia are composed of thin membrane protrusions that typically contain bundles of parallel actin filaments, rather than branched, and are used to dynamically extend and retract helping cells to sense their environment and guide migration (Goode and Eck, 2007).

Lamellipodia are based upon a thin sheet-like branched network of actin filaments, whereas filopodia are highly organized and tightly cross-linked long bundles of unidirectional and parallel actin filaments3.

According to the convergent elongation model of filopodia initiation,26,47 filopodia are formed by reorganization of the dendritic actin network, which is assembled through nucleating activity of the Arp2/3 complex (Fig. 1, top).