Cytoskeleton and Cilia

Question 1

What is the cytoskeleton ?

Answer 1

An intricate network of protein filaments that extends throughout the cytoplasm

Question 2

What are the roles of the cytoskeleton ?

Answer 2

1. Strength and support to cell
2. Allows cell shape changes
3. Cell movement (sperm)
4. Cell contraction
5. Wound healing
6. Cell division
7. Interaction with other cells
8. Organisation of cell interior

Question 3

What causes epidermolysis bullosa?

Answer 3

Caused by defects in keratin and also collagen

Question 4

What causes progeria ?

Answer 4

Caused by defects in nuclear lamin

Question 5

What are the three types of cytoskeleton filaments of eukaryotic cells?

Answer 5

1. Intermediate filaments
2. Microtubules
3. Actin microfilaments

Question 6

What is the main role of the IFs?

Answer 6

To provide tensile strength

Question 7

What are the main IFs proteins ?

Answer 7

Keratin and lamin

Question 8

What are desmosomes ?

Answer 8

Contacts points between epithelial cells

Question 9

How are cells connected to the basal laminate?

Answer 9

Via hemisdesmosomes

Question 10

What do desmosomes do?

Answer 10

They spread the stress points on a cell, to minimise damage to mechanical strain

Question 11

What secondary structure does keratin have ?

Answer 11

Alpha helix

Question 12

What is the basic unit of keratin composed of?

Answer 12

2 tetramers

Question 13

How many tetramers make up an IF filament ?

Answer 13

8

Question 14

Where does keratin usually make up the IFs?

Answer 14

Epithelia
Tongue 
Skin
Gut 
Nails
Hair

Note - cytoplasmic IFs

Question 15

What is pemphigus ?

Answer 15

It is an autoimmune condition where the body’s own antibodies attack the desmosomes which causes the contact between epithelial cells to loosen

Question 16

What type of IF is lamin?

Answer 16

Nuclear

Question 17

What is the role of lamin?

Answer 17

To provide attachment sites for DNA-binding chromatin

Question 18

How is the process of disassembly and assembly of lamin controlled ?

Answer 18

By protein phosphorylation of lamin

Question 19

What are the proteins that add and remove phosphates ?

Answer 19

Add - kinases

Remove - phosphatases

Question 20

What are microtubules made up of?

Answer 20

Tubulin proteins

Question 21

Where are microtubules anchored ?

Answer 21

Centrosome - close to the nucleus

Question 22

What are microtubules important for ?

Answer 22

1. Cell division
2. Anchoring organelles like mitochondria
3. Intracellular transport

Question 23

How many tubulin filaments are there in a microtubule?

Answer 23

13 - with alpha and beta tubulin molecules

Question 24

How could you describe the microtubules?

Answer 24

Hollow, polar structure

Question 25

Microtubules can grow and shrink independently of each other. What is this referred to as?

Answer 25

Dynamic instability

Question 26

How are microtubules regulated ?

Answer 26

G-proteins

Tubulin bind to GTP

Question 27

What happens when the GTP is hydrolysed to GDP?

Answer 27

The microtubule shrinks again

Question 28

Are tubulin polymers stable or unstable in cells?

Answer 28

Unstable

Question 29

Where is the minus end of the microtubule?

Answer 29

At the centrosome, growing out the the plus end

Question 30

Why do cilia rely on microtubules?

Answer 30

For movement

Question 31

What is the protein that allows the microtubules to move and bend?

Answer 31

Dynein

Question 32

What is a condition that is caused by defective cilia?

Answer 32

Karatagener’s syndrome

Hearing loss

Question 33

What are actin filaments involved in?

Answer 33

Cell crawling
Phagocytosis
Cell division

Question 34

How are actin filaments stabilised ?

Answer 34

Actin binding proteins

Question 35

Are actin filaments polarised ?

Answer 35

Yes

Question 36

The growing actin strand will be bound to _______ and the shrinking strand will be bound to ________

Answer 36

ATP

ADP