The Cytoskeleton: Part 1 Flashcards Preview

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Flashcards in The Cytoskeleton: Part 1 Deck (49):
1

List five functions of the cytoskeleton.

1. provides structural support
2. positions organelles
3. directs vesicular transport
4. involved in locomotion
5. required for cell division

2

What are three types of filaments that form the cytoskeleton?

1. microfilaments: actin; organized in cortical bundles
2. intermediate filaments: intermediate filament proteins provide structural support
3. microtubules: tubulin; longest component of the cytoskeleton and largest diameter

3

What is immunofluorescence?

-a technique used to determine the location of proteins within the cell; cells are fixed (not live imaging)

4

What is the difference between a primary antibody and a secondary antibody?

primary antibody: binds specifically to the protein of interest
secondary antibody: binds to the first antibody and is covalently tagged with a fluorescent molecule

5

What is a fluorescent microscope used for?

-to excite the fluorescent molecule and visualize the light emitted

6

Why does the light microscope have a resolution limit?

because of diffraction

7

What is the difference between a light microscope and an electron microscope?

light microscope: based on the wavelength of light
electron microscope: electrons, shorter wavelengths; use for finer details

8

Are electron microscope images static or dynamic?

static

9

The cytoskeleton is a ________ structure

dynamic

10

For cell motility/crawling, the actin filament must rapidly:

disassemble and reassemble

11

What does the leading edge point towards?

points towards the stimulus (e.g. A clump of bacteria)

12

Most interphase microtubules radiate from...

one microtubule organizing centre

13

Microtubules are reorganized to form the _____ _____ ____ in diving cells

bipolar mitotic spindles

14

What are cytoskeletal filaments composed of? What do they form?

-composed of small soluble subunits
-form polymers

15

How are polymers constructed?

need to be strong, flexible and easy to disassemble and reassemble

16

Single chain polymers with STRONG bonds have ____ thermal stability. Do they have dynamic filament?

high; no

17

Single chain polymers with WEAK bonds have ____ thermal stability. Do they have dynamic filament?

low; yes

18

What are two ways in which bonds can be broken in a single chain polymer?

1. breakage in the middle
2. removal from one end

19

Multiple subunits are assembled into bundles of ______

protofilaments

20

Individual protofilaments associate with each other ______

laterally

21

Strength of protofilaments is due to:

many weak bonds; each bond does not need to be as strong

22

Breakage in the middle breaks 5 _____ _____

longitudinal bonds

23

Removal from one end breaks how many longitudinal and lateral bonds?

one, two

24

Actin filaments, intermediate filaments and microtubules are all constructed of:

more than one protofilament

25

What are the three stages of actin polymerization in a test tube?

1. nucleation (lag phase): involves actin subunits coming together to create oligomers
2. elongation (growth phase): growing actin filament
3. steady state (equilibrium phase): actin filament with subunits coming on and off

26

What are five processes/functions that microtubules are involved in?

1. intracellular transport
2. structural support
3. cell organization
4, mitosis
5. cell motility (flagella and cilia)

27

Microtubules are made of... (4 things)

-tubulin, long hollow tubes, stiff, inextensible

28

Microtubules are made of individual subunits of:

alpha-tubulin
beta-tubulin

29

Two closely related globular proteins form ______ ______

tubulin heterodimers

30

What gives the microtubule polarity?

regular arrangement of alpha and beta subunits since it has a plus end (beta) and a minus end (alpha)

31

What kind of bond interactions do the individual subunits in a protofilament have?

noncovalent interactions which are relatively weak but make a fairly stable tubule

32

one tubulin heterodimer = ?

microtubule subunit

33

What makes up a hollow tubule?

13 parallel protofilaments

34

Where does growth and disassembly of microtubules occur?

the ends

35

In vitro microtubule growth is faster at the ____ ____

plus end

36

What is in vitro microtubule growth?

isolated microtubules are incubated with a high [ ] of tubulin and GTP

37

Are the newly formed microtubules at the plus or minus end?

plus; longer and faster

38

Tubulin subunits are enzymes that...
When this occurs in the filament, ____ is trapped in the tubulin subunits. Which form is this?

hydrolyze GTP
GDP
D-form

39

What is the difference between the T form and D form?

GTP bound
GDP bound

40

Microtubules have a _____ cap at the plus end when dimer addition at the plus end is...

GTP
faster than GTP hydrolysis

41

GTP cap stabilizes the plus end which favours:

tubule growth

42

Which form of dimers bind more strongly to other dimers in the tubule?

T form

43

Hydrolysis of bound GTP reduces the _____ _____ of the subunit

binding affinity

44

Which region of the microtubule is less stable?

region containing GDP tubulin dimers

45

What happens during depolymerisation? Why?

-microtubule shrinks rapidly because of curling
-curling occurs because the bonds between the heterofilament are stronger than adjacent filaments

46

In cells, microtubules are nucleated at the...

MTOC: microtubule organizing centre

47

Microtubules that radiate from MTOC are joined at which end?

minus end

48

Where do plus ends radiate out towards?

PM

49

The _______ is also a MTOC because it nucleates the formation of microtubules. The minus end is _______, and the plus end is _______ (hint: think about movement)

centrosome
stabilized
dynamic (grows and shrinks)