Cytoskeleton

Question 1

What is the cytoskeleton?

Answer 1

The cytoskeleton is a network of filaments and tubules that extends throughout a cell, through the cytoplasm, which is all of the material within a cell except for the nucleus.

Question 2

What is the function of the cytoskeleton?

Answer 2

Structural framework
Stabilize the tissue
Keeps the components in place
Pseudopodia formation
Mitotic spindles
Cytokinesis
Formation of microvilli, cilia, and flagella

Question 3

What are Microfilaments?

Answer 3

Microfilaments, also called actin filaments, are polymers of the protein actin that are part of a cell’s cytoskeleton.

Question 4

What is the role of globular actin or G-actin?

Answer 4

Helps in enzymatic reactions

Question 5

What is the role of filamentous actin or F-actin?

Answer 5

Helps in muscle contraction

Question 6

What are some characteristics of microfilaments?

Answer 6

They are flexible than microtubules

Abundant in the region beneath the cell membrane

Question 7

What is the function of microfilaments?

Answer 7

They ANCHOR intrinsic proteins of the cell membrane
They help in cellular locomotion by pseudopodia formation
They form structural core of microvilli

Question 8

What are intermediate filaments?

Answer 8

Two long chains of protein that have an N-terminal and a C-Terminal.

Question 9

How many types of IF are there?

Answer 9

Keratin
Desmin
Vimentin
Neurofilaments
Glial filaments
Lamin

Question 10

Characteristics of Keratin filaments?

Answer 10

In the epithelial cells of the skin as Tonofibrils (bundle of keratin filaments)
And they terminate on desmosomes

Question 11

Where are Vimentin filaments located?

Answer 11

Fibroblasts
Macrophages
Endothelium

Question 12

Where are desmin filaments found?

Answer 12

Z discs of the muscles

Question 13

Where are neurofilaments found?

Answer 13

Neurons

Question 14

Where are Glial filaments located?

Answer 14

Astrocytes as Glial Fibrillary Acid Protein

Question 15

Where are Lamin filaments?

Answer 15

Nuclear lamina (support the nuclear envelope)

Question 16

What are Microtubules?

Answer 16

They are made out of subunits called tubulin. Each tubulin subunit is made up of one alpha and one beta-tubulin that are attached to each other.
They make a tube-like structure.

Question 17

What is the function of Intermediate filaments?

Answer 17

They connect the nuclear membrane to the cell membrane.
They form flexible scaffolding for the cell & help it resist
external pressure.
In their absence, cell rupture more easily.

Question 18

What are the characteristics of microtubules?

Answer 18

They are polymers of tubulin which takes place in the centrosome. This polymerization requires Mg++ and GTP. The minus ends of microtubules are anchored in structures called microtubule organizing centers (MTOCs) and the plus end is the growing end.

Question 19

What do Microtubule-associated proteins (MAPs) do?

Answer 19

MAP prevents depolymerization of the microtubule

MAP assists in the intracellular movement of organelles by using ATP

Question 20

What are the functions of Microtubules?

Answer 20

1. They provide the tracks along which different
   molecular motors move vesicles & organelles from one
   part of the cell to another.
2. They also form spindle, which moves chromosomes in
   mitosis.
3. They are present in the flagella of sperm and cilia to
   provide locomotion of these structures.

Question 21

What are the examples of molecular motors?

Answer 21

Kinesin (Towards the +ve end)

Dynein (Towards the -ve end)