MCB 150 FINAL EXAM with Answers
2025-2026 Updated.
Structure of Microtubules - Answer rigid, hollow tubes made of tubulin
What is tubulin - Answer a dimer of alpha-tubulin (GTP) and beta-tubulin (GDP)
How do tubulin dimers form MTS? - Answer they polymerize, assemble mt head to tail so mt has
polarity
Which end do polymerization and depolymerization happen on MT? - Answer possible at both ends,
but usually occurs at plus end bc minus end is anchored into centrosome
What happens once there is a dimer addition to a microtubule? - Answer GTP in b-tubulin is hydrolyzed
and turned into GDP, GTP in a-tubulin is not hydrolyzed for stability
Dynamic instability and GTP cap - Answer GTP bound tubulin prevents subunits from peeling away so if
polymerization slows down GTP cap is hydrolyzed and microtubule starts depolymerizing
Tubulin + GTP - Answer = polymerization
Tubulin + no GTP - Answer = depolymerization
Does GTP bound tubulin have high or low affinity for tubulin? - Answer high
Does GDP bound tubulin have high or low affinity for tubulin? - Answer low
Colchicine and Colcemid affect on microtubules - Answer Binds tubulin->induces depolymerization-
>non-specifically affects all microtubules
, Vincristine and vinblastine affect on microtubules - Answer Binds tubulin->induces depolymerization-
>targets rapidly dividing cells
Taxol affect on microtubules - Answer binds microtubules->stabilizes microtubules->targets rapidly
dividing cells
Function of microtubules - Answer interphase cell (guiding intracellular transport), dividing cell
(segregating chromosomes during mitosis), ciliated cell (propulsion or sweeping of fluids over
membranes)
Where do new microtubules come from? - Answer mts originate from the microtubule organizing
center (MTOC)
What is major MTOC in animal cells? - Answer centrosome (origin and anchor)
What does centrosome contain? - Answer pair of centrioles, pericentriolar material
Centrioles - Answer 9 triplet arrangement of microtubules
Pericentriolar material - Answer amorphous collection of protein from which mts emanate from
Where do new mts emanate from? - Answer gamma tubulin
Microtubules associated motor proteins - Answer kinesin moves toward plus end, dynein moves
toward negative end
Examples of stable microtubules providing polarity to a cell type - Answer Neuron- extremely polarized
(one side looks way different than the other), MTS in nerve cells are not oriented the same way
2025-2026 Updated.
Structure of Microtubules - Answer rigid, hollow tubes made of tubulin
What is tubulin - Answer a dimer of alpha-tubulin (GTP) and beta-tubulin (GDP)
How do tubulin dimers form MTS? - Answer they polymerize, assemble mt head to tail so mt has
polarity
Which end do polymerization and depolymerization happen on MT? - Answer possible at both ends,
but usually occurs at plus end bc minus end is anchored into centrosome
What happens once there is a dimer addition to a microtubule? - Answer GTP in b-tubulin is hydrolyzed
and turned into GDP, GTP in a-tubulin is not hydrolyzed for stability
Dynamic instability and GTP cap - Answer GTP bound tubulin prevents subunits from peeling away so if
polymerization slows down GTP cap is hydrolyzed and microtubule starts depolymerizing
Tubulin + GTP - Answer = polymerization
Tubulin + no GTP - Answer = depolymerization
Does GTP bound tubulin have high or low affinity for tubulin? - Answer high
Does GDP bound tubulin have high or low affinity for tubulin? - Answer low
Colchicine and Colcemid affect on microtubules - Answer Binds tubulin->induces depolymerization-
>non-specifically affects all microtubules
, Vincristine and vinblastine affect on microtubules - Answer Binds tubulin->induces depolymerization-
>targets rapidly dividing cells
Taxol affect on microtubules - Answer binds microtubules->stabilizes microtubules->targets rapidly
dividing cells
Function of microtubules - Answer interphase cell (guiding intracellular transport), dividing cell
(segregating chromosomes during mitosis), ciliated cell (propulsion or sweeping of fluids over
membranes)
Where do new microtubules come from? - Answer mts originate from the microtubule organizing
center (MTOC)
What is major MTOC in animal cells? - Answer centrosome (origin and anchor)
What does centrosome contain? - Answer pair of centrioles, pericentriolar material
Centrioles - Answer 9 triplet arrangement of microtubules
Pericentriolar material - Answer amorphous collection of protein from which mts emanate from
Where do new mts emanate from? - Answer gamma tubulin
Microtubules associated motor proteins - Answer kinesin moves toward plus end, dynein moves
toward negative end
Examples of stable microtubules providing polarity to a cell type - Answer Neuron- extremely polarized
(one side looks way different than the other), MTS in nerve cells are not oriented the same way
