L18- Movement along actin filaments and microtubules

Question 1

Where do motor proteins get energy from?

Answer 1

ATP hydrolysis

Question 2

Give 3 motor protein families and the track they move along?

Answer 2

1. Kinesin- along microtubules
2. Dynein- along microtubules
3. Myosin- along actin filaments

Question 3

In which direction of microtubules do kinesin and dynein move?

Answer 3

Kinesis- towards PLUS END

Dynein- towards MINUS END

Question 4

What are the 2 types of dynein?

Answer 4

1. cytoplasmic dynein

2. axonemal dyneins- cilliary and flagellar

Question 5

What are the structures of dynein and kinesin?

Answer 5

Dynein quite complicated- looks like the uterus

Kinesin is simpler- a coiled coil

Question 6

How does ATP drive dynein and kinesin movement?

Answer 6

ADP is swapped for ATP. The ATP is hydrolysed. The next head swings to next binding site along the filament.

Question 7

How long does it take for vesicles to move down a 1m long axon?

Answer 7

about 2 days

Question 8

What facilitates membrane traffic between organelles?

Answer 8

Microtubule motors, transporting vesicles between

Question 9

How does the:

1. Er move?
2. Golgi move?

Answer 9

1. Kinesin moves the ER

2. Dynein moves the Golgi

Question 10

When are microtubules themselves cargoes for microtubule motors?

Answer 10

1. Anti-parallel sliding e,g, in mitotic and meiotic spindles.
2. Parallel sliding e.g. in cilia and flagella

Question 11

What do cilia and flagella use to do their beating movement?

Answer 11

Dyneins. Specialised stable microtubule structures called axonerves, with dynein “arms” that drive the beating

Question 12

Why do the microtubules cause beating rather than just sliding in ciliary and flagellar beating?

Answer 12

There are linker proteins that hold the microtubules together so they can bind a bit but not carry on sliding.

Question 13

What do plants, algae and fungi use for long distance organelle transport?

Answer 13

Myosins

Question 14

Which myosin is the one most found in animals and what’s its structure?

Answer 14

Muscle myosin 2

Long coiled coil which can assemble into filaments. Looks a bit like a willy

Question 15

What is the sliding filament theory of muscle contraction?

Answer 15

Myosin 2 walks along actin, using ATP.
Actin filaments slide.
The phosphate release strengthens the bonding to the binding site. The hydrolysis swings the arm back to position, sliding actin along.
Z discs brought closer together=muscle contraction.

Question 16

Where is myosin 2 found outside muscle cells?

Answer 16

IN contractile bundles called stress fibres and in the contractile ring in cell division.

Question 17

What structure does myosin 1 have?

Answer 17

Only has one head.

Question 18

What is myosin 1’s role?

Answer 18

Short distance organelle movement and cell crawling. Myosin 1 on plasma membrane drives this.

Question 19

What keeps the Golgi in the centre of the cell?

Answer 19

Dynein