Cytoskeleton

Question 1

What is the proximate cause of multicellular organisms cell shapes

Answer 1

Changes in internal organisation due to changes in cytoskeleton

Question 2

What is the ultimate cause of multicellular organisms cell shapes

Answer 2

Difference in cell structure due to changes in gene expression

Question 3

What is the role of actin filaments

Answer 3

Key in cell division, cell migration and cell contraction

Question 4

What is the main role of microtubules

Answer 4

Main role to create mitotic spindles used in cell division and present in nerve cells

Question 5

How are cytoskeleton polymers formed

Answer 5

Formed by non-covalent protein-protein interactions

Question 6

What leads to polymer formation

Answer 6

Head-to-tail association leads to polymer formation

Question 7

What is the ARP complex

Answer 7

7 sub unit protein complex and role in the regulation of actin cytoskeleton

Question 8

What occurs after the branching of nucleation via the ARP complex

Answer 8

1st step in formation of new phase/ structure via self assembly

Question 9

What is type II myosin

Answer 9

Type II myosin forms “double-headed” dimers => dimers then self assemble into bipolar thick filaments

Question 10

What is sarcomere contraction driven by

Answer 10

Myosin force generation on actin

Question 11

What are the building blocks of microtubules

Answer 11

A dimmer of alpha (a-tubulin - GTP) and beta tubulin (B-tubulin - taxol and GDP)

Question 12

What is the centrosome

Answer 12

Primary microtubules organising centre and are loose assemblies built around centrioles

Question 13

What is the effect of GDP tubulin on microtubule lattice

Answer 13

Makes microtubule lattice unstable

Question 14

What is the result of the loss of GTP cap

Answer 14

Leads to self un-peeling and microtubule catastrophe

Question 15

What are the roles of microtubules in cells

Answer 15

1) internal organisation of cell - moving vesicles + positioning organelles
2) chromosome segregation - mitotic spindle
3) moving fluids or cells in fluids - e.g cilia + flagella

Question 16

What are the roles of the cilia and flagella

Answer 16

Both used for moving fluids and moving fluids in

Question 17

What are the symptoms of kartageners syndrome and situs inversus

Answer 17

-difficulty breathing
-chronic stiffness
-male and female infertility
-situs inversus

Question 18

What are the properties of intermediate filaments

Answer 18

-high tensile strength
-resistant to treatments that disrupt actin filaments and MT
-no nucleotide binding
-assemble by coiled-coil interactions

Question 19

What is a heptad

Answer 19

7 residues

Question 20

What is nuclear lamina

Answer 20

Disassembly during cell division

Question 21

What are the kinetic effects of strong interactions

Answer 21

Strong interactions => kinetically more stable than weak interactions

Question 22

How does the process of immunofluorescence light microscopy work

Answer 22

Primary antibodies against protein of interest bound to fixed cell => fluorescent secondary antibody is used to light up the structure

Question 23

How are actin filaments formed

Answer 23

By head to tail non-covalent associated of individual actin molecules

Question 24

What does actin do in filament assembly

Answer 24

Actin binds and hydrolyses ATP during filament assembly

Question 25

Where does most of actin filament growth occur from

Answer 25

Occurs at plus ends

Question 26

What are the features which use organised microtubule arrays for directed transport

Answer 26

Proximal vs distal (neuron)
Apical vs basolateral (epithelial cells)
Center vs perimeter (pigment cell)

Question 27

What are actin filaments

Answer 27

Polar, non-covalent polymers involved in cell organisation, cell movement and basis of muscle contraction