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BIOLOGY 285 Study Guide - Quiz Guide: Tubulin, Kinesin, Microscope Slide

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lavendersnail893
16 Nov 2020
School
UMASS-Amherst
Department
Biology
Course
BIOLOGY 285
Professor
Laura Francis

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Document Summary

Dynamic instability causes microtubules either to grow or to shrink rapidly. A microtubule in its shrinking phase has lost its gtp cap and the tubulins at the ends are in the gdp form. In order to stop it from shrinking and start growing, enough gtp-subunits must be added quickly to regain its gtp cap. The rate of gtp-tubulin addition will be greater at a higher concentration of tubulin. If gdp was the only thing present in the solution, then the microtubule will continue to shrink and disappear. If the solution contained a non-hydrolysable gtp, microtubules would continue to grow until all free tubulin subunits have been used up. Please answer the following questions about this graph of a microtubule polymerization assay: how is this experiment performed (i. e. what is added, what is measured, etc?) This is an experiment on kinetics of microtubule assembly in vitro performed with purified tubulin and gtp.

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Related Questions

dynamic intability causes microtubules either to grow or shrink rapidily. consider an individual microtubule that is in its shrinking phase

1. what might happen at the end of the microtubule in order for it to stop shrinking and start growing.

2. How would an increase in tubilin concentration affect this switch from shrinking to growing.

3.what woul happen if GTP were present in the solution.

4. what would happen if the solution contained an analog of GTP that could not be hyrdolyzed?

Activity: Dynamic Instability of Microtubules

Part A

What causes catastrophe of the microtubule in vitro?

the lack of tubulin heterodimers
non-motor Microtubule Associated Proteins (MAPs)
GTP hydrolysis
mutation of the β-tubulin

Part B

What is the role of GTP in microtubule polymerization?

GTP binds the alpha and beta tubulin subunits together to form the tubulin monomer.
GTP hydrolysis provides the energy for the polymerization of the microtubule.
GTP is a second messenger that signals the need for polymerization/de-polymerization.
GTP stabilizes the tip of the microtubule, allowing more monomers to be added.

Part C

What would happen in the treadmilling experiment if a non-hydrolyzable analogue of GTP were used?

The monomers would be unable to add to the plus end, and the microtubules would shrink until they disappeared.
The microtubule would treadmill until the new tubulin, with non-hydrolyzable GTP, reached the minus end, and then it would only extend at the plus end.
The microtubule would add monomers at both the plus and minus ends, growing in both directions.
The non-hydrolyzable GTP would stabilize both ends, causing treadmilling to stop.

Part D

What is the difference between the plus and minus ends of the microtubule in in vitro experiments?

The beta subunit of the tubulin is exposed on the minus end.
Polymerization occurs at the plus end.
The plus end has a lower critical concentration for tubulin heterodimers.
Catastrophe occurs at the minus end.

Part E

How would the drug taxol affect the in vitro dynamic instability and treadmilling experiments?

Taxol would block catastrophe at the plus end in the dynamic instability experiment but not depolymerization at the minus end in the treadmilling experiment.
Taxol would block the addition of tubulin in both experiments, leading to a destruction of the microtubules.
Taxol would stabilize the microtubules in both experiments, leading to polymerization without catastrophe.
Taxol would block depolymerization at the minus end in the treadmilling experiment but not catastrophe at the plus end in the dynamic instability experiment.

Dynamic instability causes microtubules to grow and shrink rapidly. Consider a microtubule that is in its shrinking phase. Why is it shrinking, and what must happen at the end of the microtubule for it to stop shrinking and start growing?