Lecture 21- Cytoskeleton Toxins

Question 1

What are the three major types of filaments that make up the cytoskeleton?

Answer 1

Microtubules
F-Actin
Intermediate Filaments

Question 2

Which cytoskeletal filament resist compression?

Answer 2

Microtubules

Question 3

Which cytoskeletal filaments resist tension?

Answer 3

F-Actin and intermediate filaments

Question 4

Which cytoskeletal filament move chromosomes during mitosis?

Answer 4

Microtubules- move the chromosomes into the middle of the cell during prophase and they move the separated chromosomes to the poles of the cell during anaphase.

Question 5

Which cytoskeletal filament divides cell during cytokinesis?

Answer 5

Microtubules and Actin filaments

Question 6

What are the four ways that toxins can affect the cytoskeleton?

Answer 6

1. Toxins can promote the formation of protein filaments
2. Toxins can interfere with the promotion of protein filaments
3. Toxins can promote the breakdown of protein filaments
4. Toxins can interfere with the breakdown of protein filaments

Question 7

How does taxol affect the cytoskeleton? (What mechanism)

Answer 7

Taxol inhibits/ interfere with the normal breakdown of microtubules into tubulin.

If you put a bunch of taxol the MTs will form (it will grow outwards but not inwards). They’ll grow and get stuck (repeat) and eventually you’ll just have a big ball of MTs in the cell.

Question 8

When you add taxol, what is the consequence for cells? (I.e, which phase of the cell cycle does it get stuck?)

A. G1 phase
B. S phase
C. G2 phase
D. Mitosis
E. Cytokinesis

Answer 8

Mitosis- bc one of the functions of MTs is to move the chromosomes.

Question 9

Significance of taxol

Answer 9

It is used to treat certain cancers (inappropiate cell reproduction) by inhibiting mitosis

Question 10

How does Colchine affect the cytoskeleton?

Answer 10

Interfere/ inhibit the formation of microtubules from the tubulin subunits

Question 11

What is the consequence of the addition of colchine? (In which phase of the cell cycle does the cell get stuck?)

Hint: similar to taxol

Answer 11

Mitosis

Question 12

What is the significance of Colchine?
(Significance of its derivative- Colcemid)

Answer 12

Colcemid- used to prepare chromosomes

Ex: we take human blood cells, we allow them to grow in the presence of this MT inhibitor, they’ll go from G1 -> G2 then they get stuck at metaphase and we can use that to observe human chromosomes from cells that have been stuck in metaphase.

Question 13

What is the effect of Phalloidin in cytoskeleton?

Answer 13

Phalloidin inhibits the breakdown of F-actin into G-actin

Question 14

What is a phalloidin?

Answer 14

An organic molecule made by an organism to kill off things that would otherwise try and eat it.

Question 15

Significance of Phalloidin

Answer 15

It is used in fluor microscopy

Phalloidin is covalently attached to a fluorescent dye which is why the actin filament is green.

Question 16

What fluorescent dye labels the mitochondria and why does it stick to the mitochondria?

Answer 16

Mitotracker red- it both fluoresces red and has an affinity for its target.

Target: any membrane that has a charge across it.

The inner mitochondrial membrane has a charge across it bc of ETC. The mitotracker red will stick to this membrane.

Question 17

How does polyacrylamide affect the cytoskeleton?

Answer 17

It promotes the breakdown of intermediate filaments to keratins.

Question 18

Significance of adding polyacrylamide

Answer 18

The strength of axons comes from intermediate filaments

Question 19

consequence of adding polyacrylamide

Answer 19

It kills sensory neurons