CELL ORGANELLES 3

CILIA AND FLAGELLA

• hair-like outgrowths of the cell membrane.
• help in cell movement.

• Core of cilia and flagella is called the axoneme -- have number of microtubules running parallel to the long axis.
• The axoneme usually has nine pairs of doublets of radially arranged peripheral microtubules, and a pair of centrally located microtubules -- 9+2 arrangement.

• The central tubules are connected by bridges and is also enclosed by a central sheath -- connected to one of the tubules of each peripheral doublets by a radial spoke -- nine radial spokes.
• The peripheral doublets are also interconnected by linkers.
• Both the cilium and flagellum emerge from centriole-like structure called the basal bodies.

CENTROSOME AND CENTRIOLES

• Centrosome is an organelle usually containing two cylindrical structures called centrioles.
• Both the centrioles in a centrosome lie perpendicular to each other.
• Each centriole is made up of nine evenly spaced peripheral fibrils of tubulin.
• The central part of the centriole is also proteinaceous and called the hub, which is connected with tubules of the peripheral triplets by radial spokes made of protein.

• Function- 1. The centrioles form the basal body of cilia or flagella, 
• 2. spindle fibres that give rise to spindle apparatus during cell division in animal cells