Flashcards in The Cytoskeleton: Part 1 Deck (49):
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
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
What is immunofluorescence?
-a technique used to determine the location of proteins within the cell; cells are fixed (not live imaging)
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
What is a fluorescent microscope used for?
-to excite the fluorescent molecule and visualize the light emitted
Why does the light microscope have a resolution limit?
because of diffraction
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
Are electron microscope images static or dynamic?
The cytoskeleton is a ________ structure
For cell motility/crawling, the actin filament must rapidly:
disassemble and reassemble
What does the leading edge point towards?
points towards the stimulus (e.g. A clump of bacteria)
Most interphase microtubules radiate from...
one microtubule organizing centre
Microtubules are reorganized to form the _____ _____ ____ in diving cells
bipolar mitotic spindles
What are cytoskeletal filaments composed of? What do they form?
-composed of small soluble subunits
How are polymers constructed?
need to be strong, flexible and easy to disassemble and reassemble
Single chain polymers with STRONG bonds have ____ thermal stability. Do they have dynamic filament?
Single chain polymers with WEAK bonds have ____ thermal stability. Do they have dynamic filament?
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
Multiple subunits are assembled into bundles of ______
Individual protofilaments associate with each other ______
Strength of protofilaments is due to:
many weak bonds; each bond does not need to be as strong
Breakage in the middle breaks 5 _____ _____
Removal from one end breaks how many longitudinal and lateral bonds?
Actin filaments, intermediate filaments and microtubules are all constructed of:
more than one protofilament
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
What are five processes/functions that microtubules are involved in?
1. intracellular transport
2. structural support
3. cell organization
5. cell motility (flagella and cilia)
Microtubules are made of... (4 things)
-tubulin, long hollow tubes, stiff, inextensible
Microtubules are made of individual subunits of:
Two closely related globular proteins form ______ ______
What gives the microtubule polarity?
regular arrangement of alpha and beta subunits since it has a plus end (beta) and a minus end (alpha)
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
one tubulin heterodimer = ?
What makes up a hollow tubule?
13 parallel protofilaments
Where does growth and disassembly of microtubules occur?
In vitro microtubule growth is faster at the ____ ____
What is in vitro microtubule growth?
isolated microtubules are incubated with a high [ ] of tubulin and GTP
Are the newly formed microtubules at the plus or minus end?
plus; longer and faster
Tubulin subunits are enzymes that...
When this occurs in the filament, ____ is trapped in the tubulin subunits. Which form is this?
What is the difference between the T form and D form?
Microtubules have a _____ cap at the plus end when dimer addition at the plus end is...
faster than GTP hydrolysis
GTP cap stabilizes the plus end which favours:
Which form of dimers bind more strongly to other dimers in the tubule?
Hydrolysis of bound GTP reduces the _____ _____ of the subunit
Which region of the microtubule is less stable?
region containing GDP tubulin dimers
What happens during depolymerisation? Why?
-microtubule shrinks rapidly because of curling
-curling occurs because the bonds between the heterofilament are stronger than adjacent filaments
In cells, microtubules are nucleated at the...
MTOC: microtubule organizing centre
Microtubules that radiate from MTOC are joined at which end?
Where do plus ends radiate out towards?