The Cytoskeleton

Question 1

What are the three filament types of the cytoskeleton?

Answer 1

1. Microtubules
2. Microfilaments
3. Intermediate filaments.

Question 2

What are the functions, components, and diameter of microtubules?

Answer 2

• Movement and support.
• Made up of the protein tubulin.
• The diameter is about 25nm.

Question 3

What are the functions, components, and diameter of microfilaments?

Answer 3

• Movement and support.
• Made up of the protein Actin
• The diameter is about 6nm.

Question 4

What are the functions, components, and diameter of intermediate filaments?

Answer 4

• Support.
• Made up of various proteins.
• The diameter is about 10nm.

Question 5

What are the two ends of the microtubules called?

Answer 5

The plus end and the minus end.

Question 6

Which end of the microtubules grows the fastest?

Answer 6

The plus end.

Question 7

What end of the microtubules are anchored close to the centrioles?

Answer 7

The minus end.

Question 8

In what cellular structures can you find microtubules?

Answer 8

In cilia and in centrioles.

Microtubules fuse side by side to form doublets or triplets

Question 9

What microtubule structures do cilia contain?

Answer 9

9 peripheral doublets (18 microtubules fused together in pairs)
2 central microtubules.

Question 10

What microtubule structures do a centriole contain?

Answer 10

9 peripheral triplets.

Question 11

What is a centrosome?

Answer 11

A centrosome is a pair of centrioles.

Question 12

In which cases are microfilaments stable?

Answer 12

In cell-cell junction, microvilli, terminal web in epithelial cells, thin myofilaments in muscle cells.

Question 13

What is the function of the motor enzymes (motor proteins)?

Answer 13

Motor enzymes walk along the cytoskeletal filaments transporting vesicles of compounds. They are together with the microtubules responsible for the intracellular movement of vesicles, organelles, and chromosomes.

Question 14

What motor enzyme walks toward the + end of the microtubules?

Answer 14

Kinesin

Question 15

What motor enzyme walks toward the - end of the microtubules?

Answer 15

Dynein

Question 16

What motor enzyme does the actin filaments (microfilaments) cooperate with?

Answer 16

Myosin.

Question 17

Which end of the actin does the myosin walk towards?

Answer 17

The + end

Question 18

What motor enzymes does the intermediate filaments cooperate with?

Answer 18

None. The intermediate filaments do not participate in movement in the cell and their only function is to reinforce the cell structure and participate in cell-cell junctions. Hence, do not cooperate with any motor enzymes.

Question 19

What proteins do you find in the intermediate filaments of epithelial cells?

Answer 19

Keratins (>40 subtypes)

Question 20

What proteins do you find in the intermediate filaments of muscle cells?

Answer 20

Desmin

Question 21

What proteins do you find in the intermediate filaments of connective tissue cells?

Answer 21

Vimentin

Question 22

What proteins do you find in the intermediate filaments of neurological cells?

Answer 22

Glial fibrillar acidic protein

Question 23

What proteins do you find in the intermediate filaments of nerve cells?

Answer 23

Neurofilament proteins.

Question 24

What proteins do you find in the intermediate filaments of the inner lining of nuclear envelopes in all cells?

Answer 24

Nuclear lamins A, B

Question 25

What induces and controls the growth of cytoplasmic microtubules in the MTOC - microtubule-organizing center?

Answer 25

The centrioles and the surrounding material containing tubulin G.

Question 26

What are microfilaments built up of?

Answer 26

Microfilaments are built up by F-actin (formed by G-actin)

Question 27

What are some pigment granules found in the cytoplasm of the cell?

Answer 27

1. Melanin

2. Lipofuscin