Microubules

Question 1

Microtubules are built from?

Answer 1

Tubulin

Question 2

Each is itself a ..?

Answer 2

Dimmer

Question 3

Composed of????????

Answer 3

Alpha and beta tubulin :o

Question 4

Bond?

Answer 4

Bonded tightly together by non covalent interactions.

Question 5

It is made of …

Answer 5

13 parallel protofilaments

Question 6

Structure?

Answer 6

Each protofilament has a structural polarity with alpha tubulin exposed at one ens and beta tubulin at the other

Question 7

Ends?

Answer 7

Beta tubulin + end
Alpha tubulin - end

Question 8

Where do they grow out from?

Answer 8

Centrosome

Question 9

They extend towards?

Answer 9

Cell periphery

Question 10

What do they create?

Answer 10

A system of tracks within the cell along which vesicles, organelles and other components can be transported

Question 11

Function?

Answer 11

They are responsible for transporting and positioning membrane enclosed organelles within the cell and for guiding the intracellular transport of various cytosolic macromolecules
Cell shape and movements
Separation of chromosomes in Mitosis

Question 12

Centrosome structure

Answer 12

Centrosome organizes an array of microtubules that radiates outward through the cytoplasm, it consists of a pair of centrioles surrounded by a matrix of proteins

Question 13

What does the centrosome include??

Answer 13

In includes hundreds of ring shaped structures formed from gamma tubulin.

Question 14

Gamma tubulin function ?

Answer 14

Each one serves as a starting point or nucleation site for the growth of one microtubule.

Question 15

What do Alpha beta tubulin have to do with gamma tubulin ?

Answer 15

Alpha- beta tubulin dimers add to each gamma tubulin ring complex in specific orientation, minus end is embedded in the centrosome and growth only occurs at the plus end that extends into cytoplasm.

Question 16

Once a microtubule is nucleated…

Answer 16

Dynamic instability occurs, it starts growing outward To the center by adding AB tubulin dimers to plus end then it can undergo transition that causes it to shrink inward by losing tubulin from its free plus then start growing again or disappear completely or be replaced by a new microtubule that grows from the same gamma tubulin. It’s also called polymerization and depolymerization.

Question 17

How can a microtubule be prevented from disassembling?

Answer 17

by attaching plus end to another molecule or cell structure to prevent depolarization.

Question 18

The dynamic instability stems from the capacity of tubulin dimers to hydrolyze GTP, explain:

Answer 18

Tubulin carrying GTP bind more tightly to one another that tubulin dimers carrying GDP. Therefore rapidly growing plus ends of microtubules.
From time to time especially when growth is slow, GTP will be hydrolyzed to GDP before fresh dimers
Loaded with GTP have time to bind.
GDP dimers are less tightly bound tin the polymer, protofilaments peel away from the plus end, dimers
Are released causing microtubules to shrink.

Question 19

Microtubules dynamics can be modified by :

Answer 19

Drugs

Question 20

Microtubules organize the cell interior ?

Answer 20

Hell ye

Question 21

All microtubules in the axon point in the same-

Answer 21

Direction

Question 22

Their plus ends are toward the-

Answer 22

Axon terminal

Question 23

How does that help

Answer 23

Cell is able to transport organelles , membrane vesicles macromolecules from the cell body to the axon terminal or in the opposite direction.

Question 24

Movement of cytoplasm and organelles are driven by :

Answer 24

Motor proteins

Question 25

How do motor proteins work?

Answer 25

They use energy derived from repeated cycles of ATP to travel steadily along cytoplasmic microtubules

Question 26

Two families of motor proteins :

Answer 26

Kinesins that move toward the plus end of the microtubule.( outward from the cell body).
Dyneins that move toward the minus end.(toward cell body).

Question 27

How do motor proteins move along microtubules
?

Answer 27

using their globular heads which bind and hydrolyze ATP and interact with microtubules and a single tail at the other end which interact with cargo.

Question 28

The heads interact with microtubules in a stereospecific manner, so that ..

Answer 28

motor protein will attach to a
microtubule in only one direction.

Question 29

The tail of a motor protein generally binds stably to some cell component,
such as a vesicle or an organelle, and thereby..

Answer 29

determines the type of cargo that the motor
protein can transport.

Question 30

Do cilia and flagella contain stable microtubules?

Answer 30

Hell ye

Question 31

Cilia and flagella contain stable microtubules and are moved by

Answer 31

Dynein

Question 32

Cilia and flagella beat in a

Answer 32

Whiplike fashion

Question 33

Why do cilia and flagella move in a whiplike motion

Answer 33

either to move fluid over the surface of a cell or propel single cells through a fluid, locomotion, collecting food.

Question 34

How does flagella or cilia move?

Answer 34

It performs a repetitive cycle of movements consisting of a power stroke (cilium is extended and fluid is driven over the surface of cell); followed by recovery stroke(cilium curls back into position with minimal disturbance to the surrounding fluid.

Question 35

How long does each cycle require?

Answer 35

0.1 - 0.2 second and generates a force parallel to cell surface.

Question 36

Heredity defects ciliary dynein causing:

Answer 36

Kartagener’s Syndrome (men are infertile because sperm is nonmotile and they have an increased susceptibility to bronchial infections because their respiratory cilia tract are paralyzed.

Question 37

Nine triplets of microtubules result in:

Answer 37

Centrioles(star shaped)

Question 38

9 doublets+2. Additional result in:

Answer 38

Cilia and flagella (wheel shaped)

Question 39

Movements of cilium or flagellum is produced by

Answer 39

bending of its core as they slide against each other.

Question 40

What’s associated with microtubules?

Answer 40

accessories proteins that are found across the microtubule

Question 41

Accessories protein function ?

Answer 41

They serve as links to hold the bundle together, other generate the force needed to bend. Heads carry two rows of dynein molecule appearing like arms reaching toward adjacent doublet microtubule.

Question 42

Ciliary dynein is attached by its _______ to one microtubule while its ________ interact with an adjacent microtubule to generate a sliding force between two microtubules

Answer 42

1- tail
2- two heads

Question 43

It the outer doublet microtubules and their associated dynein molecules are freed from other components of a sperm flagellum and then exposed to ATP :

Answer 43

DOUBLETS SLIDE AGAINST EACH OTHER

Question 44

In an intact flagellum-

Answer 44

Doublets are tied together by flexible protein links so that the action of the system produces bending.