Microtubule are looks like minute tubules.
Discovery: Ledbetter and Porter in 1963 discovered microtubules.
Structure: They are long, unbranched, hollow tubular and usually, a diameter of 10 to 20 mμ.
Functions:
(i) It gives mechanical support to cytoplasm.
(ii) It forms spindle fibres during cell division
(iii) It accelerates movement of water and different ions outside and inside the cell.
(iv) It plays a mentionable role in keeping the size of cell
(v) Cytoplasmic organelles are attached to microtubules.
