Cytoskeletal Structures of the Cells! Biological Sciencess !!

Cytoskeltal structures

These are fibrous or fine tubular structures which form the supportive structures of the cell. These are of three types
microtubules,
microfilaments
Intermediate filaments

(a) Microtubules

discovered by Robertis and Franchi, (1953) term coined by Slautterback (1963), are unbranched hollow non contractile tubules of indefinite length, 25 nm in thickness with 15 nm core and formed of 13 helically arranged protofilaments of a and b-tubilin protein. Microtubules grow from nucleating
centres. Microtubules are basic structures of spindle apparatus, centrioles, basal
bodies, cilia and flagella and are responsible for cell motility and maintenance of shape.

Their tips can grow and shorten quickly. GTP, Ca2+, Mg2+ and a calmodulin bound protein are required for assembly. Colchicine prevents it.
Microtubules are basic structures of spindle apparatus, centrioles, basal bodies, cilia and flagella. They are also present in other cellular structures like sensory hair, nerve processes, sperm tail, etc. Microtubules present in cytoplasm provide shape and polarity to cells. Microtubules are absent in procaryotes (except Anabaena),Amoeba and Slime Moulds.

(b) Microfilaments 

They are cylindrical solid, contractile rods or filaments of actin and myosin protein with a diameter of 6 to 10 nm. Microfilaments can form hexagonal
bundles, take part in cytoplasmic streaming, membrane undulations, cleavage, contraction of muscles, movement of microvilli to absorb food and endocytosis.

(c) Intermediate Filaments

They are intermediate in size having diameter around 10-15 nm and are composed of non-contractile proteins. Intermediate fibres (IF) are of four types–keratin filaments, neurofibrils, glial filaments and heterogeneous filaments (viz., desmin filaments, vimentin filaments, synemin filaments).They privide rigidity to cell and maintains the cell structure

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