Cytoskeleton

Question 1

What is the cytoskeleton and what is it made from?

Answer 1

Structure within the cell.
Actin –> thinnest filament
intermediate filaments –> for mechanical strength (keratin anchored to plasma membrane at desmosomes in cells that need strength)
Microtubules –> thickest filament. Minute hollow tubes.

Question 2

What are the different types of intermediate filaments?

Answer 2

nuclear - mesh like structure - nuclear lamins found in all animal nuclei.
Cytoplasmic - rope like structure: keratin filaments (in epithelial cells), vimentin (in connective tissue), nuclear filaments (in nerve cells)

Question 3

What diseases can form when intermediate filaments are mutated?

Answer 3

Keratin filament mutation = Epidermolysis bulls simplex = blistering skin
Nuclear lamins mutation = Hutchinson’s disease

Question 4

Structure of microtubules

Answer 4

Hollow tube made of heterodimer (alpha and beta tubulin).
rigid - rupture when stretched.
One end attached to the organising centre (centrosome) and grow outwards.
Polar - has a positive (fast growing) and negative end (slow growing)

Question 5

How to microtubules assist cell movement?

Answer 5

Motor proteins - microtubules provide tracks for vesicles and organelles to follow.
Kinesins and dyneins are motor proteins that associate with microtubules.
tail interacts with the cargo being transported and the globular had interacts with the microtubules, it attached and detaches using ATP allowing the motor protein to “walk” along the microtubule.
Kinesin moves to the positive end. Dynein moves to the negative end.

Question 6

Cilia, flagella and microtubules

Answer 6

Cytoskeleton provides stiff support within these structures. (the cilia and the rest of the cell)
Sperm = one long cilia - used to propel the cell.
Cilia around the oviduct to wave the egg through.

Question 7

Structure of actin filaments

Answer 7

Actin monomers pack tightly and form 2 helices that can assemble and disassemble. The filaments can cross link, like in the cell cortex to give strength and change the shape. Thinnest of the filaments

Question 8

Function of actin

Answer 8

Essential fro cell movement
involved in the support of microvilli (found in the intestine to increase the SA of the plasma membrane so more proteins at the surface.
Involved in muscle contraction
Drives cell movement.
Forms the contractile ring in cell division