Cytoskeleton

Question 1

What are the 3 filaments of the cytoskeleton?

Answer 1

Microfilaments
Intermediate filaments
Microtubules

Question 2

What are the functions of microfilaments?

Answer 2

Whole-cell movement
Muscle contraction
Cell shape
Cytokinesis

Question 3

What is the function of intermediate filaments?

Answer 3

Strength

Question 4

What are the functions of microtubules?

Answer 4

Movement of cilia and flagella
Intracellular trafficking
Mitotic spindle formation

Question 5

What is the central component of microfilaments and how is it formed?

Answer 5

Actin
G-actin monomers polymerize into F-actin microfilament using ATP

Question 6

What are the functions of actin?

Answer 6

Structural and motility systems
Maintain cell shape
Support for plasma membranes and its protrusions
Restricts diffusion of organelles
Anchor for cell adhesion molecules
Contraction (myosin) in muscle cells
Actomyosin ring in telophase of mitosis

Question 7

How do cells migrate on ECM with actin?

Answer 7

Leading edge attaches and back edge releases

Important during embryogenesis and growth

Question 8

What are thin filaments?

Answer 8

Mainly F-actin, particularly in muscle cells
Tropomyosin
Troponin complex (skeletal and cardiac cells)

Question 9

What is myosin?

Answer 9

Thick filament
Actin-binding motor protein
Binds ATP
Muscle and non-muscle cells

Question 10

What is the function of intermediate filaments?

Answer 10

Mechanical strength

Question 11

What are the major types of intermediate filaments?

Answer 11

Keratins
Vimentins
Neurofilaments
Lamins
Nestin

Question 12

Where keratins found and what is there function?

Answer 12

In cytosol of epithelial cells

Interconnect desmosomes
Strong adhesion between epithelial cells and underlying ECM

Question 13

What are the functions of neurofilaments?

Answer 13

Structural support in nerve axon to resist breakage

Question 14

What is vimentin and its function?

Answer 14

Includes desmin and vimentin
In mesoderm-derived cells, widely distributed
Desmin in muscle cells - stabilize contractile apparatus

Question 15

Where are lamins found and what are their function?

Answer 15

Only in nuclei

Line inner nuclear surface
Protect chromatin from mechanical stress
Support nuclear envelope

Dissemble at mitosis

Question 16

Where is nestin found and what is its function?

Answer 16

Widely expressed, particularly neural progenitor cells
Associated with cell proliferation

Question 17

What is the structure of microtubules?

Answer 17

Cytosolic
Hollow
Polar
Cylinders
Alpha and beta tubulin heterodimers

Question 18

What are the functions of microtubules?

Answer 18

Motility (cilia and flagella)
Chromosomal movements during cell division
Transport of intercellular vesicles

Question 19

How to microtubules redirect traffic?

Answer 19

By disassembling in one region and assembling in another

Question 20

What is a centrosome and its function?

Answer 20

Composed of 2 centrioles and pericentriolar material
Origin of microtubules, cap minus end

Question 21

What is dynamic instability of microtubules?

Answer 21

Assembly then breakdown - rapid
Tubulin bound to GTP add at plus end
Disassembly from plus end - prevented by capping

Question 22

What is vesicle and organelle transport?

Answer 22

Requires ATP and microtubule motor proteins (ATPases)
Kinesin - anterograde
Cytoplasmic dynein - retrograde

Question 23

How do cilia and flagella move?

Answer 23

Axoneme - 9+2 extending from basal body anchored in plasma membrane
Axonemal dynein - ATPase
Stable microtubules resist breakdown

Question 24

What is the function of microtubules in mitosis?

Answer 24

Two centrosomes