BMS02-1004 Cytoskeleton

Question 1

What is cell polarity?

Answer 1

Movement of the cell and inside the cell

Question 2

What shape protein is actin?

Answer 2

Globular

Question 3

What forms actin filaments?

Answer 3

G-actin

Question 4

Why is it important that actin filaments are polar?

Answer 4

To give it a + and - end

Question 5

How are monomers added to the actin filament?

Answer 5

ATP has to be hydrolysed to the ADP

Question 6

Give 3 functions of actin

Answer 6

Mechanical support
Cell motility
Cell shape changes and maintenance

Question 7

How can we stop G actin polymerising?

Answer 7

Actin-sequestering proteins such as profiling and thymosin

Question 8

Give some examples of intermediate filaments?

Answer 8

Keratin in epithelia

Neurofilamin

Question 9

What’s the function of intermediate filaments?

Answer 9

Forms lamins which give structure and transcriptional regulation
Anchors cells at junctions

Question 10

How are intermediate filament polymers formed?

Answer 10

Monomer forms a helical dimer, 2 of these join to form a tetramer, tatramers link up in a staggered formation to form the filament

Question 11

Which features of the cytoskeleton can assemble quickly?

Answer 11

Microtubules and actin

Question 12

What makes up a microtubule?

Answer 12

Alpha and beta tubulin

Question 13

What gives microtubules polarity?

Answer 13

One end is alpha and the other is beta

Question 14

How does actin cause movement? (3)

Answer 14

Push out protrusions at the front of the cell as actin polymerise

These adhere to focal adhesions (macromolecules) giving contractile force

The cell pulls against the anchorage point to move the cell forwards

Question 15

What holds vesicles near the membrane?

Answer 15

Actin

Question 16

Describe the movement of myosin and actin in muscles

Answer 16

Calcium binds to tropomyosin moving it away to reveal the myosin binding site on actin
Myosin binds and ATP is converted to ADP so the myosin tails moves
ADP is released so the myosin head relaxes and detaches

Question 17

How does chemo affect the cytoskeleton?

Answer 17

Destabalise microtubules so cells can’t divide

Question 18

What can diseases involving actin cause?

Answer 18

Deaf and blindness

Question 19

What is epidermolysis bullosa simplex?

Answer 19

Mutations in keratin impacting the epidermis making the skin very sensistive

Plectin mutations can also cause this (giant protein with links to filaments, actin and tubules)

Question 20

What is amyotrophic lateral sclerosis

Answer 20

Mutations in neurofilaments causing motor neuron degredation

Question 21

What causes alzhiemers?

Answer 21

Tangled neurofilaments so microtubules can’t bind

Question 22

What causes hereditary spastic paraplegia?

Answer 22

A mutations which causes an enzyme to sever microtubules

Question 23

What does listeria bacteria do?

Answer 23

The cell engulfs it but the bacteria escapes from the vesicle, actin then polymerises on the bacteria so it’s active and can go into other cells

Question 24

What does the vaccinia virus do?

Answer 24

The virus is engulfed but escapes from the vesicle, it replicates and microtubules carry it to the edge, actin then polymerises so it can escape from the cell

Question 25

How can and can’t intermediate fibres move?

Answer 25

They can bend but they cant stretch