The Importance? Important for support of the cell No cytoskeleton means NO CELL Especially important for animal cells because they lack cell walls Allows cell to move Moving is key to the survival of the cell
Both movement within the cell and changes in cell location Vital to the survival of all cells Can dismantle itself and reform in a different part of the cell which allows for the cell to change shape Enabled by motor molecules sliding microtubules or microfilaments past one another
Motor molecules attached to one microtubule slide it past another. Sliding of neighboring microtubules moves cilia and flagella. Motor molecules can also slide microfilaments Motor proteins can “walk” the organelles
Both are used for locomotion in the cell, though differ in length, number, and beating pattern However, have same interior structure, involving microtubules and proteins
Cilia have a back and forth motion It creates a waving motion to propel the cell forward Usually occur on surface of cell in large amounts.
AA flagella uses a whipping like motion to propel the cell in desired direction SSimilar to a snakes movement UUsually only 1 to a few per cell
Microtubules Hollow rods, with diameter of approximately 25 nm Made up a of a protein called tubulin Shape and support the cell Also make up tracks for dyenin arms to move organelles throughout the cells (like railroads) Can disassemble and reassemble in different parts of the cell
Microfilaments (Actin Filaments) solid rods about 7 nm in diameter called actin filaments, because they made of the protein actin. Present in all eukaryotic cells In animal cells, such as intestinal cells, where things need to be transported across the membrane, bundles of microfilaments make up the inside of microvilli.
Microfilaments A microfilament is a twisted double chain of actin subunits Help support the cells shape by holding tension and creating 3- D networks similar to tree branches These networks give outer cytoplasm of a cell the consistency of a gel, which is different than the more liquid state of the interior cytoplasm
Microfilaments They are either straight rods or structures similar to a large tree branch with several smaller branches extending off of it.
Microfilaments & Motility Microfilaments are well known for their role in cell motility because they make up an essential part of muscle cells. Thousands of actin filaments are laid next to each other along the muscle cell, along with thicker filaments made of a protein called myosin. Mysosin has little “arms” that move down the actin filaments (microfilaments) and cause muscle contraction by shortening the length of the muscle cell. (Smaller versions of this exist in many other cells which causes motility within the cell)
Pseudopodia This same concept is used by amoebas for movement. --amoebas move by a process called pseudopodia which is when they extend a “foot” out and then flow into that foot. The contractions that allow this movement are when networks of actin filaments disassembling and reassembling in a new place and actin filaments work with myosin filaments to squeeze the cytoplasm into the new area. (some white blood cells and other animal cells move similarly) Also, the myosin and actin interactions, coupled with movement of actin filaments cause cytoplasmic streaming, or a flow of cytoplasm around the cell which helps materials get to their destination more quickly (like a lazy river for cell nutrients)
Intermediate Filaments Diameter 8–12 nm (the intermediate diameter between microfilaments and microtubules, hence the name) Provide framework for the entire cytoskeleton. Used to bear tension, like microfilaments. Diverse type of cytoskeleton (there are numerous kinds of intermediate filaments) Each type is constructed from a different type of protein in a certain family (includes the keratins) more permanent than microfilaments and microtubules, even after cell death they still exist (like dead skin cells) Important in reinforcing the shape of the cell and in anchoring certain organelles. -- The nucleus, for instance, is held in a “cage” of intermediate filaments that are anchored in the cytoplasm by other intermediate filaments. (when shape is necessary for function intermediate filaments are key in retaining that shape) -- For example, the long extensions (axons) of nerve cells that send signals are held in place by a type of intermediate filament.
Diseases Many neurodegenerative diseases, such as Alzheimer’s disease may be associated with dysfunction of cytoskeletal components In Alzheimer’s disease, certain defects in a protein stimulate structural alterations in the cytoskeleton of neurons, which causes the neurons to lose the shape that is instrumental in performing their function.
And more diseases… Another disease that is caused by a malfunctioning cytoskeleton is Duchenne Muscular dystrophy Duchenne muscular dystrophy is when a mutation in the dystrophin gene causes the cytoskeleton in certain cells to become inable to anchor itself on a membrane. This causes the cell to lose its structure and the cell membrane to let everything in, which causes the cell to “explode.”