Cell migration

Question 1

List the core function of the cytoskeleton

Answer 1

1) It forms the shape of the cell and provides mechanical strength

2) Allows for cell locomotion through the lamellapodia and the filapodia

3) Drives cell division

4) Organises the organelles in the cell

5) Drives intracellular transport via motor proteins

Question 2

What are motor proteins and how do they perform their functions

Answer 2

Motor proteins are proteins that organsie organelles in the cell to appropriate locations

• They bind to polarised cytoskeletal filaments and use ATP to move

Question 3

How do different motor proteins differ from each other

Answer 3

1) The filament they bind to

2) The direction at which they move along

3) The molecules they carry

Question 4

What is the motor protein that binds to actin filament and what does it do

Answer 4

Myosin ( specifically mysodin II)

• It generates a contractile force in muscle and non-muscle cells

Question 5

Describe the structure of mysoin II

Answer 5

• A thick bipolar filament
• 300 myosin head that oragnsie themselves into a head to tail format

Question 6

Describe the process of the structural changes used by myosin to walk on the filament

Answer 6

Attactched
1) Myosin head which lacks ATP is tightly bound to the filament

Released
2) ATP from ATP-Actin complex binds to the myosin and causing a change in conformation of actin site hence myosin detatches

cocked
3) ATP is hydrolysed to ADP and this results in the movement of the lever arm. ADP stores inorganic P

Force Generating
4) The myosin head binds to a new site in the filament which wil trigger the release of P. The release of P results in a power stroke.

Question 7

How does the actin- myosin complex apply to muscle contraction

Answer 7

• muscle fibres contain sarcomeres
• Thin filament = actin filament
• Thick filament = myosin II
• The actin plus end is anchored at the Z disc
• Mysoin walks toward the plus end
• This means that contraction happens towards the minus end

Question 8

What does titin do

Answer 8

It provides elasticity

Question 9

How does Ca+ play a role in muscle contraction

Answer 9

CA2+ ion is released by the sarcoplasmic reticulum

• This triggers the contraction of the myofibril

Question 10

Name another myosin protein

Answer 10

Myosin V
They alk along the actin filament and transport organelles

Question 11

Name the motor proteins taht bind to microtubules

Answer 11

1) Kinesins
2) Dyneins

Question 12

What is the function of Kinesins and how do they perform their function

Answer 12

• Kinesins are responsible for carrying cell material form the the centre of the cell to the cell periphery
• Kinesin moves towards the plus end

1) There are two types of heads : The rear head is tightly bound to the microtuble
and ATP . Lead head is loosely bound to ADP

2) Dissociation of ADP and Hydrolysis of ATP causes a power stroke

Question 13

Dyneins

Answer 13

• They move towards the minus end
• They are the largest and fastest motor proteins

Question 14

Name the 3 types of dyneins

Answer 14

1) Cytoplasmic dyneins 1: Spindle fibre formation, mRNA trafficking and organelle traficking

2) Cytoplasmic dyneins 2: They are responsible for intraflagellar transport

3) Axonemal dyneins : Cilia/ flagella beating

Question 15

Describe the microtubule organisation / polarity

Answer 15

Plus end - cell periphery

minus end - centrsome

kinesin = outward
dyneins = inwards

Question 16

list the importance of cell migration

Answer 16

essential for
1) Nervous system dvelopment
2) immune response
3) Bone remodelling
4) Wound healing
5) Cancer metastatis

Question 17

Describe the importance of cell polarity in cell migration

Answer 17

• The cells need to know where they need to migrate to. They have to dofferentiate between top and bottom or left and right
• Cells build distinct molecular structures at the front/ back that establishes polarity

Question 18

What is cell polarity controlled by ?

Answer 18

1) External signals
2) Actin cytoskeleton
3) Rho GPTase
- Rac
- Ro
- Cdc42

Question 19

Describe the processes invloved in cell crawling

Answer 19

1) Protrusion
* Actin polymerisation pushes the cell membrane forward
* This forms the lamellopodia and filopodia
- This occurs at the leading edge where Arp2/3 forms branched network = lamellopodia causing it to spread and formin forms unbranched network = filopida cause it move forward

2) Attatchment
Actin connects to the substrate via intergrins
This forms focal adhesions

3) Traction
The bulk of the cytoplasm is drawn forward

Question 19

Describe the role of Myosin II in cell migration

Answer 19

1) Matures the focal adhesions
2) Generates tension
3) Pulls rear of the cell forward
4) Prevents lateral protrusion

Question 19

What is the role of microtubules in cell migration

Answer 19

1) Maintains polarity
2) Positions centrosome
3) Guide focal adhesion turnover

4) Transport signalling molecule