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The cytoskeleton is a complex, dynamic network of interlinking protein filaments present in the cytoplasm of all cells, including those of bacteria and archaea. [2] In eukaryotes, it extends from the cell nucleus to the cell membrane and is composed of similar proteins in the various organisms.
Illustration of a eukaryotic cell membrane Comparison of a eukaryotic vs. a prokaryotic cell membrane. The cell membrane (also known as the plasma membrane or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of a cell from the outside environment (the extracellular space).
Detailed diagram of lipid bilayer of cell membrane. The cell membrane, or plasma membrane, is a selectively permeable [citation needed] biological membrane that surrounds the cytoplasm of a cell. In animals, the plasma membrane is the outer boundary of the cell, while in plants and prokaryotes it is usually covered by a cell wall.
Cell biology (also cellular biology or cytology) is a branch of biology that studies the structure, function, and behavior of cells. [1] [2] All living organisms are made of cells. A cell is the basic unit of life that is responsible for the living and functioning of organisms. [3] Cell biology is the study of the structural and functional ...
Other cellular extensions that protrude from the cell membrane are known as membrane protrusions or cell protrusions, also cell appendages, such as flagella, and microvilli. [ 8 ] [ 9 ] Microtentacles are cell protrusions attached to free-floating cells, associated with the spread of some cancer cells .
Inside a cilium and a flagellum is a microtubule-based cytoskeleton called the axoneme. The axoneme of a primary cilium typically has a ring of nine outer microtubule doublets (called a 9+0 axoneme), and the axoneme of a motile cilium has two central microtubules in addition to the nine outer doublets (called a 9+2 axoneme).
Specialized cells are usually characterized by a very specific cortical actin cytoskeleton. For example, in red blood cells, the cell cortex consists of a two-dimensional cross-linked elastic network with pentagonal or hexagonal symmetry, tethered to the plasma membrane and formed primarily by spectrin, actin and ankyrin. [9]
Cells have developed several types of junctional complexes to serve these functions, and in each case, anchoring proteins extend through the plasma membrane to link cytoskeletal proteins in one cell to cytoskeletal proteins in neighboring cells as well as to proteins in the extracellular matrix. [6]