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NTA AbhyasNTA Abhyas 2020Cell : The Unit of Life
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Solution:
Structure of a centriole.
(i) A centriole possesses a whorl of nine evenly spaced peripheral fibrils of tubulin. It is absent in the center. Therefore, the arrangement is called a 9+0.
(ii) Each fibril is made up of three sub-fibres. Therefore, it is called triplet fibril named A, B, C.
(iii) The adjacent triplet fibrils are inter-connected by C-A proteinaceous linkers.
(iv) The centre of the centriole possesses a rod-shaped proteinaceous mass known as a hub. From the hub, nine proteinaceous strands are developed towards the peripheral triplet fibrils. These strands are called radial spokes.
(v) Due to the presence of peripheral fibrils and radial spokes, the centriole gives a cartwheel appearance.
(vi) There is no membrane boundary for a centriole, but it is surrounded by pericentriolar satellites, also known as massule.
