Cilia and Flagella

Cilia and Flagella

1. Several cell types use microtubules

   • Flagella undulate like snake to move cells forward e.g.sperm tail
   • Cilia move back and forth, have a rapid power stroke and a slow recover stroke

2. Microtubules, hollow made of tubulin, job of maintaining the shape and cell motility, move chromosomes in cell division and organelle movement

   • Made of α and β tubulin dimers
   • One end is -Ve and other is +ve
   • Microtubules have 3 types of structures, singlet (cytoplasm & mitotic spindle), doublet (Cilia and flagella), Triplets (centrioles and basal bodies)

3. Moving vesicles along microtubule in nerve axons needs kinesin and cytosolic dyein motor proteins

   • Both Kinesin and dyein have ATPase head and tail to bind to vesicles
     • Kinesin helps forward movement of vesicles to synapse
     • Cytosolic dyein mediates backward movement to cell body along singlet microtubule
     • At synaptic endings motor proteins send NT along actin microfilaments

4. Cilia have a 9+2 structure of microtubules, covered by plasma membrane

   • flagella have same structure but are longer

5. Dyein have 2/3 heads to hydrolyse ATP and make bonds to adjacent microtubule

   • Able to bend and rotate towards basal body

6. Centrioles made up of 27 stable microtubules, but 9+0 structure and triplet surrounded by protein matrix

   • Become organising centres forming the microtubule spindles

7. Microtubule spindles used to pull apart chromatids in cell division, Motor proteins promote chromosome movement along microtubules

   • Microtubules dismantled by kinetochores to release tubulin subunits

8. Both anchored in cells by basal body