Cilia, Flagella and Mitochondria 18/11/19
Microtubules – Hollow, large – α and β Tubulin = protein subunits
- Cylindrical – β and α = bind together
- Dynamic – grow and shrink – responds to cellular signals
- Constant polymerisation/depolymerisation – adding/removing tubulin dimers (chem
compound – 2 similar subunits) – GTP hydrolysis
- Green filaments = microtubules
- Originate from ‘microtubule organisation centre’
- Bigger than intermediate filaments
- close to nucleus
3 structures:
- 1 cylinder = singlet – cytoplasm/mitotic spindles
- 2 cylinders = doublet – cilia/flagella
- 3 cylinders = triplet – centrioles/basal bodies
Structure depends on required function – e.g. – centrioles need lots of strength so 3, but flagella need
to move – less strength needed
Grow out from centrosome – (near nucleus) – anchored in place with triplet
Have a role in cell division
- Partition of replicated chromosomes
- Assembles and disassembles microtubule structure – forms mitotic spindle
- Centromere changes shape/structure – pulls chromatids
- 9 triples (27) microtubules – surrounded by protein matrix
- 9+0 = no tubules in centre
- Centriole pairs form mitotic spindle – so equal division of genetic material
Mitotic spindle controls chromosome movement
- 2x centrosomes (replication) – opposite poles of cell
- Microtubules grow out of them
Centrosome at prometaphase = Aster
- Tubules = down to midline and attached to kinetochore – attaches to chromatin
- Microtubules shorten (anaphase) – depolymerise at kinetochore ends – sister chromatids
more to opposite ends of cell
- Breaks down of microtubules = pulling motion
- Kinetochore breaks down microtubules – releases tubulin subunits
Microtubules – Hollow, large – α and β Tubulin = protein subunits
- Cylindrical – β and α = bind together
- Dynamic – grow and shrink – responds to cellular signals
- Constant polymerisation/depolymerisation – adding/removing tubulin dimers (chem
compound – 2 similar subunits) – GTP hydrolysis
- Green filaments = microtubules
- Originate from ‘microtubule organisation centre’
- Bigger than intermediate filaments
- close to nucleus
3 structures:
- 1 cylinder = singlet – cytoplasm/mitotic spindles
- 2 cylinders = doublet – cilia/flagella
- 3 cylinders = triplet – centrioles/basal bodies
Structure depends on required function – e.g. – centrioles need lots of strength so 3, but flagella need
to move – less strength needed
Grow out from centrosome – (near nucleus) – anchored in place with triplet
Have a role in cell division
- Partition of replicated chromosomes
- Assembles and disassembles microtubule structure – forms mitotic spindle
- Centromere changes shape/structure – pulls chromatids
- 9 triples (27) microtubules – surrounded by protein matrix
- 9+0 = no tubules in centre
- Centriole pairs form mitotic spindle – so equal division of genetic material
Mitotic spindle controls chromosome movement
- 2x centrosomes (replication) – opposite poles of cell
- Microtubules grow out of them
Centrosome at prometaphase = Aster
- Tubules = down to midline and attached to kinetochore – attaches to chromatin
- Microtubules shorten (anaphase) – depolymerise at kinetochore ends – sister chromatids
more to opposite ends of cell
- Breaks down of microtubules = pulling motion
- Kinetochore breaks down microtubules – releases tubulin subunits
