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BIO130H1 Lecture Notes - Lecture 8: Epithelium, Desmosome, Intermediate Filament

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maroongerbil498
18 May 2012
School
UTSG
Department
Biology
Course
BIO130H1
Professor
Jane Mitchell

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BIO130H1 Full Course Notes
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BIO130H1 Full Course Notes
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Document Summary

But when gtp is lost the microtubule shrinks really fast. This is because the individual protofilaments have weak bonds they separate when the cap is lost. But since the mico-dimers have strong bond, they stay together. And these leads to curling!! (the er and golgi are located in the cell body) *motor proteins use atp to move along the microtubules for transporting organelles. By the signal they can change their direction. Treadmillling range: at one point there, they reach a critical concentration(equilibrium) D. in a band that moves from the plus to the minus end. (this couljd be ans if it is pulse! Myosinii along actin filaments causes muscles to contract. A. dynein (to position near nucleus, it should move to ends,,,, so it is dynein) Myosin ii (+ end directed: microtubule motor proteins: They all couple atp hydrolysis with conformational changes to generate force. All move in a specific direction along filaments that have polarity (plus/minus end).

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Related Questions

  1. Are there benefits to the arrangement of a microtubule into 13protofilaments? How are the subunits of F-actin and microtubulesheld together?

1 Stathmin and Profilin are similar because ____.

a) Stathmin and Profilin are necessary to form branched actin filaments

b) Stathmin is necessary for nucleation of microtubules as Profilin is necessary for forming straight unbranched actin filaments

c) Stathmin is used to sequester free tubulin subunits as Profilin is used to sequester free actin monomers

d) Stathmin and Profilin are motor proteins

2 Which of the following statements regarding dynamic instability is FALSE?

a) Dynamic instability is required for both actin and microtubule function.

b) The GTP cap helps protect a growing microtubule form depolymerization.

c) GTP hydrolysis by the tubulin dimer promotes microtubule shrinking.

d) Cap proteins help stabilize the microtubules, promoting microtubule growth.

3. Which of the following statements about vesicular membrane fusion is TRUE?

a) Membrane fusion does not always immediately follow vesicle docking.

b) The interactions of the v-SNAREs and t-SNAREs pull the vesicle membrane and the target organelle together so that their lipids can intermix.

c) NSF and SNAP disassemble the SNARE complex so the SNAREs can be recycled.

d) All of the above are true.

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.