The Cytoskeleton

Question 1

What are the X2 different types of actin?

One is a polymer of the other, but which is which?

Answer 1

F-actin is a polymer of G-actin

F = filamentous

G = globular

Question 2

What is the shape of the monomer G-actin?

Answer 2

Butterfly shaped

Question 3

How do actin filaments form?

How do they degrade?

Answer 3

G-actin requires ATP to polymerise

It can bind to either end, but the filament has a positive and negative end and polymerisation occurs more rapidly at the positive end

As time passes ATP is hydrolysed to ADP which increases susceptibility to depolarisation

Question 4

How do intermediate filaments form?

What is their monomer?

Answer 4

Their monomers are intermediate filament proteins

X2 IF proteins form a helical dimer

X2 helical dimers form X1 IF unit tetramer

Question 5

What is the monomer of microtubules?

What are each of these made up of?

Which end is negative and which is positive?

Answer 5

Tubulin

= X1 alpha Tubulin = negative
= X1 beta Tubulin = positive

Question 6

How many molecules of Tubulin make up the microtubule circumference?

Answer 6

X13

Question 7

How do microtubules assemble?

Does this require energy?

How do they degrade?

Answer 7

Tubulin monomers bind to GTP and join the GTP rich cap (+ve end) of the microtubule polymer

Over time the GTP hydrolyses to GDP and these GDP bound monomers dissociate rapidly

Question 8

What protein links all X3 of these cytoskeleton components together?

Answer 8

Plectin

Question 9

What type of structures show actin based movement?

Answer 9

Lamellipodia

Question 10

Through what do lamellipodia adhere to the ECM?

What protein do they use to attach themselves to the ECM?

Answer 10

Focal contact junctions or focal adhesions

Integrins

Question 11

What structures use microtubule based movements?

Answer 11

Cilia

Question 12

What microtubule associated protein attaches to X1 microtubule of one pair and one of the neighbouring pair to climb up it in order to create the cilia style movements?

Answer 12

Dyenin

Question 13

What of the X3 protein filaments are involved in the movement of synaptic vesicles and other intracellular cargo along their filaments?

Which associated proteins aid in this function? Name X2 and state which end of the protein filament they transport towards.

Answer 13

Microtubules

Dyenin = towards the negative end

Kinesin = towards the positive end

Question 14

What is the name given to dyenin and kinesin relating to the fact that they do not become un-attached from the microtubule when transporting molecules?

Answer 14

Processive motor proteins

Question 15

Name a non-processive motor protein.

Why is it non-processive?

Answer 15

Myosin

During its movements it detaches