Microtubules

Question 1

What are the general roles of microtubules?

Answer 1

Structural support, cell division, intracellular transport, cell motility, cell polarity

Question 2

Both alpha and beta tubulin bind to GTP. But how is this relationship different for the two tubulins?

Answer 2

Only beta tubulin can hydrolyse the bound GTP to GDP and exchange GDP for GTP.

Question 3

How is microtubule polarity determined?

Answer 3

Head to tail arrangement of alpha beta tubulin heterodimers results in a crown of alpha tubulin signifying the negative end and a crown of beta tubulin signifying the positive end

Question 4

In a microtubule, which end is the crown of beta tubulin?

Answer 4

The positive end

Question 5

In a microtubule, which end is the crown of alpha tubulin?

Answer 5

The negative end

Question 6

In non-polarised animal cells, which end of a microtubule is usually associated with MTOCs?

Answer 6

The negative end (alpha-tubulin crown)

Question 7

In non-polarised animal cells, which end of a microtubule usually extends towards the cell periphery (away from MTOCs)?

Answer 7

The positive end (beta-tubulin crown)

Question 8

What are most microtubules nucleated by? Where are they?

Answer 8

Gamma-tubulin ring complexes, located in the pericentriolar material of an MTOC

Question 9

What is the purpose of gamma-tubulin?

Answer 9

Provides a binding site for alpha beta - tubulin dimers and the ring complex structure provides a template for nucleating microtubule formation.

Question 10

Which end of the microtubules has a higher critical concentration for tubulin concentration?

Answer 10

Negative end

Question 11

Which end of the microtubules has a lower critical concentration for tubulin dimer concentration?

Answer 11

Positive end