Cytoskeleton

Question 1

Do prokaryotic and eukaryotic cells have the following?
Cytoskeleton, intracellular movement

Answer 1

Prokaryotic cells have none
Eukaryotic have both

Question 2

what is the cytoskeleton?

Answer 2

The network of protein filaments that provides structural framework also plays a role in cell movement and mitosis

Question 3

How is the cytoskeleton dynamic?

Answer 3

Can dismantle in one spot and reassemble in another to change cell shape

Question 4

what structure organizes the cytoplasm?

Answer 4

Cytoskeleton

Question 5

Which of the following play a role in signalling?
Microfilaments, Microtubules, Intermediate filaments

Answer 5

All

Question 6

What are the subunits of Microfilaments and microtubules

Answer 6

Microfilaments: Actin
Microtubules: ab-tubulin dimers

Question 7

What is the diameter, structure and function of the following:
microfilaments
intermediate filaments
microtubules

Answer 7

Microfilaments: 7-9 nm, double helix, maintain cellular shape
Intermediate filaments: 10 nm, two anti-parallel helices/dimers (tetramers), maintain internal tridimensional structure of the cell
Microtubules: 25 nm, polymer of tubulin subunits, intracellular transport, alpha and beta tubulin

Question 8

Are the filaments (microtubules included) permanent structures?

Answer 8

No they are dynamic.

Question 9

What is G-actin and F-actin

Answer 9

G-actin are the subunits that come together to form microfilaments
G-actin polymerizes to form F-actin

Question 10

Are microtubules and microfilaments polar or non-polar?

Answer 10

Polar

Question 11

which end of microfilaments grow faster

Answer 11

the plus end

Question 12

Where are actin filaments nucleated?

Answer 12

nucleated at the plasma membrane

Question 13

What is the strongest filament

Answer 13

intermediate filament

Question 14

what are the four classes of intermediate filaments? where are they found?

Answer 14

Cytoplasmic: Keratins (epithelial cells), Vimentins (in connective tissue, muscle cells and glial cells), Neurofilaments (nerve cells)

Nuclear: Nuclear lamins (all animal cells)

Question 15

what role does microtubules play in mitosis?

Answer 15

mitotic spindle

Question 16

How do microtubules affect kinesin and dynein?

Answer 16

controls directionality

Question 17

What is taxol?

Answer 17

Anticancer drug which stops mitosis

Question 18

Which polarized end are subunits added to in microtubules?

Answer 18

Plus end

Question 19

How many protofilaments are in a tubulin monomer

Answer 19

13 laterally associated protofilaments

Question 20

which direction does kinesin and dyneins move on a microtubules?

Answer 20

Kinesins towards the plus end
Dynein towards the negative end

Question 21

what are the 3 types of junctions

Answer 21

anchoring, tight, gap

Question 22

adhesiveness of cadherin depends on what

Answer 22

Calcium and cadherin transgene

Question 23

What is EMT

Answer 23

epithelial-to-mesenchymal transition, nonmotile epithelial cells to motile cells

Question 24

How is E-cadherin activity affected by EMT and cancer progression

Answer 24

Adhesion is lost, activity decreases

Question 25

What are the main differences between classical and desmosomal cadherin?

Answer 25

Classical: two specialized cadherins: desmoglein and desmocolin Desmosomal: interact with adaptor proteins such as plakoglobin

Question 26

What are hemidesmosomes?

Answer 26

Specialized cell-matrix adhesion structures that are associated with the keratin cytoskeleton

Question 27

What are tight junctions (kissing points)

Answer 27

Permeability barriers prevent free exchange of solutes Maintain polarity by separating the apical and basolateral ends Made up of plasma membrane proteins

Question 28

What are the main integral membrane proteins in tight junctions

Answer 28

Occludin: dispensable Claudins: indispensable

Question 29

What are claudins

Answer 29

Code 20-27 kda protiens wiht four transmemebrane proteins Involved in Signaling pathways by C-terminal interaction

Question 30

Structure and function of gap junctions

Answer 30

Cylinders of six dumbbell-shaped connexin molecules Allow passage of ions and molecules smaller than 1200 Da transmission in heart for muscle contraction