Intermediate filaments

Question 1

What are the main proteins of intermediate filaments ?

Answer 1

Keratin,vimentin,lamin

Question 2

Where does the name of the intermediate filament come from ?

Answer 2

The size of the filaments in muscle (intermediate between actin and myosin )

Question 3

Intermediate filaments form a network of fibres inside the cells that provides …

Answer 3

tensile strength(think of desmosomes)

Question 4

What can IF allow cell to resist?

Answer 4

External forces such as stretching

Question 5

What are the toughest fibres in the body ?

Answer 5

Intermediate filaments (think of hair or nails)?Keratin or vimentin or lamin ?

Question 6

What is intermediate filaments also involved in ?

Answer 6

Tethering cells to other cells e.g. epithelial cells in skin ,gut,lung etc(so does this restrict movement?)

Question 7

What do intermediate filaments also do?cell contacts

Answer 7

Intermediate filamenst strengthen cell contacts via the desmosomes .

Question 8

How do Intermediate filaments give skin its strength and elasticity ?

Answer 8

Intermediate filaments fibres connect cells to each other via contact points called desmosomes.
Desomosomes allow epithelial cells to form sheets that perform vital barrier functions for the body .Desosomes spread thebstress points to minimise damage due to mechanical strain .

Question 9

What are intermediate filaments made of ?

Answer 9

IF are made of long twisted polymers of protein subunits.Monomers bind together to form dimers.Dimers bind together to form staggered tetramers .Tetramers can pack together END TO END(READ Diagrams in detail

Question 10

IF are made of long twisted polymers of protein subunits

Answer 10

-IF Tetramers packed together can go on to form a ‘helical array’ containing 8 strands of tetramers
That twist together to form a ropelike IF (E).

IFs are made of long twisted polymers of protein subunits (2)
-this structure gives the IF great strength and resistance to mechanical stress

Question 11

Do intermediate filaments provide a strong cytoskeleton ?

Answer 11

Yes, the network of intermediate filamnets desomosomal junctions become tensed and limit stetching in response to external forces .

Question 12

What happens if IFs and desmosome were not present?

Answer 12

The cells would rupture

Question 13

What do all tyoes of intermediate filaments involve?

Answer 13

They involve polymers of proteins that combine to form filaments

Question 14

What are the different cell types and their corresponding IF ?CYTOPLASMIC

Answer 14

Keratins -in epithelia - tongue,skin,gut,nails,hair
Vimentin and vimentin related -in connective tissue muscle cells,and neuroglial cells
Neurofilaments-in nerve cells

Question 15

What type of intermediate filament does the nucler have ?

Answer 15

Nuclaer lamins -all animal cells

Question 16

Discuss how the nucleus is strengthened by special IF called lamins

Answer 16

-IFs on the nuclear lamina line inner face of the nuclear envelope and provide attachment sites for DNA-binding chromatin.
-nuclear lamina disassembles and reforms each time the cell divides (mitosis/meiosis)
-this disassembly/assembly is controlled by protein phosphorylation of lamins
lamins lamins
P P P
Assembled nuclear lamina (non-dividing cells)
Disassembled nuclear lamina (dividing cells)