Differentiate among microtubules, microfilaments and microfibrils.
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They are cylindrical tubes,20-25 mm in diameter. They are composed of subunits of the protein tubulin. Microtubules act as a scaffold to determine the shape of the cell and direct movements of vesicles and other cell organelles.They form the spindle fibres for separating chromosomes during mitosis. They help in the motion of flagella and cilia when arranged in a specific pattern.
These are fine, thread-like protein fibres, 3-6 nm in diameter. They are composed predominantly of contractile proteins called actin. Microfilaments in association with protein myosin produce muscle contractions.They also carry out cellular movements like gliding and cytokinesis.
They are very fine fibrils, consisting of glycoproteins and cellulose.The structure of microfibril has the 9+2 pattern in which two central profibrils are surrounded by nine other pairs.Cellulose microfibrils are laid down in the inner surface of the primary cell wall. They provide tensile strength to the cell wall. Defect in glycoprotein component of fibrils causes Marfans syndrome,