The cytoskeleton is a network of protein fibres running through the cytoplasm of eukaryotic cells. It is not fixed: its fibres are constantly assembled and broken down as the cell needs them.Three types of fibre
• Microfilaments: the thinnest fibres (about 7 nm), made of the protein actin. They are found especially just under the cell surface membrane. With the motor protein myosin they cause movement, for example the contraction of muscle, the pinching in two of an animal cell after division, and the movement of white blood cells.
• Intermediate filaments: rope-like fibres (about 10 nm) made of various proteins, such as keratin. They are very strong and give the cell mechanical strength, anchoring the nucleus and holding cells together in tissues.
• Microtubules: the widest (about 25 nm), hollow tubes made of tubulin. They form the tracks along which organelles and vesicles are moved, make up the spindle in cell division, and form the core of cilia, flagella and centrioles.
Functions of the cytoskeleton
• support: gives the cell its shape and mechanical strength
• holds organelles in position
• transport within the cell: motor proteins, using energy from ATP hydrolysis, 'walk' along microtubules carrying vesicles, for example from the Golgi apparatus to the cell surface membrane
• movement: of chromosomes in cell division, of cilia and flagella, and of whole cellsBecause motor proteins need ATP, cells that move many vesicles or beat cilia also need many mitochondria.
• Microfilaments: the thinnest fibres (about 7 nm), made of the protein actin. They are found especially just under the cell surface membrane. With the motor protein myosin they cause movement, for example the contraction of muscle, the pinching in two of an animal cell after division, and the movement of white blood cells.
• Intermediate filaments: rope-like fibres (about 10 nm) made of various proteins, such as keratin. They are very strong and give the cell mechanical strength, anchoring the nucleus and holding cells together in tissues.
• Microtubules: the widest (about 25 nm), hollow tubes made of tubulin. They form the tracks along which organelles and vesicles are moved, make up the spindle in cell division, and form the core of cilia, flagella and centrioles.
Functions of the cytoskeleton• support: gives the cell its shape and mechanical strength
• holds organelles in position
• transport within the cell: motor proteins, using energy from ATP hydrolysis, 'walk' along microtubules carrying vesicles, for example from the Golgi apparatus to the cell surface membrane
• movement: of chromosomes in cell division, of cilia and flagella, and of whole cellsBecause motor proteins need ATP, cells that move many vesicles or beat cilia also need many mitochondria.