Microtubule Motor Protiens And Cilia/flagella

Question 1

In regards to transport why are microtubules important

Answer 1

The transport membranous vesicles from one membrane compartment to another (ex, ER to golgi)

Transport non membrane bound cargo such as rna ribosomes or cytoskeletal elements

Question 2

What are motor protiens

Answer 2

They use atp hydrolysis to make mechanical forces that move it and the cargo it’s carrying along the cytoskeleton

Move unidirectionally in a stepwise way

Question 3

What are some examples of the cargo that motor protiens carry

Answer 3

Membranous vesicles

Non membrane bound material (rna, ribosomes)

Organelles (lysosome,mitochondria)

Chromosomes

Other cytoskeletal filaments

Question 4

What are the three types of motor protiens

Answer 4

Microtubule motor protiens: walk on microtubules

Kinesins

Dyenins

Actin motor protiens: walk on actin

Myosins

Question 5

What is the kinesin 1 superfamily

Answer 5

Just called kinesin and it’s a tetramer made of two heavy chains and 2 light chains intertwined

It has a globular head which bind to microtubules and move through ATP hydrolysis

Has a tail that bind to an adapter that binds to the cargo it’s carrying

Question 6

The sequences of the kinesin globular head are

The sequences of the kinesin tails are

Answer 6

Conserved, same across other kinesin family’s

Diverse, diff evertime

Question 7

How does the kinesin motor protien move along the microtubule

Answer 7

It moves toward the positive end of the tubule with the head only interacting with the beta tubulins

The leading head hydrolyzes one atp to make ADP and Pi which give energy for the power stroke that swings the trailing head (behind) forward

So per one ATP hydrolysis is one step

This moves the motor protiens 8nm ahead (length of one tubulin dimer)

Question 8

Kinesin movement is highly processive, what does this mean

Answer 8

It can move large distances without falling off

It’s speed is proportional to the ATP concentration (max speed of 1micrometer per second)

Question 9

One microtubules head is always attached to the tubules this is called the

Answer 9

Hand over hand movement

Question 10

What is the structure of dynein

Answer 10

It’s head is 10x larger than kinesins, it walks faster too (larger steps)

It has two heavy chains and many intermediate/light chains

It has a tail that binds to that cargo though the adaptor protien dynactin

Has a globular head that generates force and atp hydrolysis to move

Question 11

Which way does dynein move

What is its role

Answer 11

Toward the minus (alpha tubulin) end of the microtubule

It positions the spindle and moves the chromosome during mitosis

Positions organelles and vesicles

Question 12

What is the retrograde and anterograde movement of the motor protein across the microtubules

Answer 12

Retrograde is moving from the + end to the - end of the microtubule (Dyneins)

Anterograde is moving from - to + (kinesins)

Question 13

Kinesins and dyenins move ____

Answer 13

Similar things in opposite direction on the same microtubule

Question 14

What is the postive run , pause , and negative run of motor protiens

Answer 14

Kinesins and dynein are both attached to the cargo, during the postive run the Kinesins are in control and moving to the + end

If it wants to change directions, the pause occurs and then the negative run where dynein take ms controls and moves towards the negative end

Question 15

What are cilia and flagella

Answer 15

Hairlike organelles that protect outward from many eukaryotic cells

The have the same structure but different functions

Different from bacterial flagella

Question 16

What is cilia specifically

Answer 16

Motile cilia move fluid (ex. In the respiratory tract they sweep mucus away from lungs)

They are very abundant on the cells surface

Have coordinated beating (power stroke and recovery stroke)

Question 17

What is flagella

Answer 17

They help the entire cell move

Question 18

What is the structure of cillia/flagella

Answer 18

The cillia/flagella are both extend out and continue from the cells plasma membrane

The axoneme makes up the cillia/flagella protrusions

The main microtubule organizing centre (centrosome) is at the basal body (which is the - end (the bottom)

The plus end is the distal end (the part sticking out)

Question 19

What is the axonemes structure

Answer 19

2 microtubules in the centre

9 microtubule A and B doublets around them (9 + 2 array)

The doublets are connected to each other through nexin

Question 20

What actually makes the cillia and flagella move

Answer 20

The axonemal dynein (dynein in cillia/flagalla) has its tail anchored to the A tubule in the microtubule doublets

It has its stalks (head) bound to the B tubule on a doublet next to it

The A tubule is like the cargo, so the dynein moves toward the negative end and move the a tubule with it during the power stroke atp hydrolysis

Question 21

How do the cillia and flagella doublet microtubules stop from just completely sliding off each other

Answer 21

Nexin (the thing that binds the doublets to each other) stops them

Basically a push and pull mechanism