Cytoskeleton 2

Question 1

Describe the centrosome:

Answer 1

The centrosome is a fibrous matrix with two centrioles, which divide to produce cilia and flagella.
They organize the matrix and allocate it to daughters during cell division.
The centrosome uses its microtubules array to sense cell boundaries and position itself at the centre providing a reference point for organelles like Golgi apparatus

Question 2

What does a centriole consist of?

Answer 2

A centriole consists of 9 sets of triplet microtubules linked together by nexin

Question 3

Describe the structure of cilia:

Answer 3

Tiny hair-like appendages
Surrounded by plasma
membrane
Have a bundle of microtubules at their core

Question 4

Describe the structure of the cilia from cross section:

Answer 4

The axoneme, the microtubule core of a cilium, is composed of 9 special doublet microtubules, fused together into a ring.
The microtubules extend continuously along the axoneme, with nexin and ciliary dynein connecting them.
Composed of one complete (A microtubule) and one partial microtubule
(B microtubule) fused together, with a pair of single microtubules at the centre

Question 5

What are flagella?

Answer 5

Flagella are hair-like cellular appendages that have a bundle of microtubules at the centre
Longer than cilia

Question 6

Describe the structural features of intermediate filaments:

Answer 6

IFs are flexible, tensile-strong cells with a Coiled Coil structure that facilitates close packing and lateral associations.
They can be stretched to over 300% of their original length without breaking.
IFs are prominent in cells subjected to mechanical stress, characterised by blistering in genetic diseases affecting keratin

Question 7

What is the structure of intermediate filament monomers?

Answer 7

Intermediate filament monomers are all highly elongated fibrous proteins
Consist of an amino-terminal head, a carboxyl-terminal tail, and a central rod domain
The rod domain consists of an extended α-helical region containing long tandem repeats called heptad repeats

Question 8

What is the nuclear lamina?

Answer 8

The nuclear lamina is a meshwork of intermediate filaments that lines the inside of the inner nuclear membrane
Interrupted at the nuclear pores

Question 9

Describe the assembly of intermediate filaments:

Answer 9

The assembly of IF involves single polypeptides with an extended central alpha-helical domain, forming parallel coiled-coil dimers.
These dimers then associate to produce a tetramer, the soluble subunit of Ifs.
Proto-filaments consist of chains of tetramers, packed together in a helical array.

Question 10

What diseases are associated with defects in the laminate proteins

Answer 10

Laminopathies and progerias

Question 11

How does laminate damage affect telomeres?

Answer 11

A-type lamins maintain telomere structure and function, stabilize 53BP1, and contribute to DNA damage response.
Loss alters telomere distribution, shortens telomeres, and increases genomic instability.