Lecture 10 - The cytoskeleton

Question 1

Function (4)

Answer 1

Shape of cell.
Intracellular movement/ location of organelles.
Modify cells in response to environmental cues.
Cell Movement.

Question 2

Contents of the cytoskeleton (3)

Answer 2

Actin filaments.
Intermediate filaments.
The micro tubules.

Question 3

How the cytoskeleton work (5)

Answer 3

The various filaments are made of monomers that continually polymerise and depolymerise.

1. The cell receives a signal (via receptors on cell membrane etc.).
2. Existing filaments in the cell depolymerise to form free monomers.
3. The monomers rapidly diffuse.
4. The monomers reassemble at a new site.

Question 4

Accessory proteins regulate (3)

Answer 4

Nucleation: The site and rate of filament formation.
(de)polymerisation.
Function.

Question 5

Cell migration (6)

Answer 5

1) Cell pushes out protrusions at the front.
2) Actin polymerisation.
3) Protrusions adhere to the surface.
4) Intergrins (link actin filaments to extracellular matrix surrounding the cell).
5) Cell contraction and retraction of the rear part of the cell.
6) Interaction between actin filaments and myosin.

Question 6

Intermediate filaments basics (6)

Answer 6

Toughest filaments - resistant to detergent and high salt.
Form a network through the cytoplasm joining up to cell-cell junctions (desosomes).
Rope like structure with many long strands twisted together and made up of different subunits.
Intermediate size (8-12 nm) between actin and microtubules.

Question 7

Intermediate Filaments basics (6)

Answer 7

Toughest filaments - resistant to detergent and high salt.
Form a network through the cytoplasm joining up to cell-cell junctions (desosomes).
Rope like structure with many long strands twisted together and made up of different subunits.
Intermediate size (8-12 nm) between actin and microtubules.

Question 8

Intermediate Filaments - IFBP (10)

Answer 8

Stabilise and reinforce IF into 3D networks.
Synamin and Plectin - Binds Desmin and Vimentin. Binds IF to other compounds (actin and microtubules). Cell to cell contact structures, desosomes.
Filagrin - Binds kertain filaments into bundles.
Plakins - Keep contact of desosomes in epithelial cells.

Question 9

Intermediate Filaments - In the nucleus (7)

Answer 9

In every eukaryotic nucleated cell.

Mesh like structures.

Question 10

Microtubules - Structure (11)

Answer 10

Long and hollow, made of tubulin.
Stiff and thick.
Thickest filaments - 25 nm. 
Each filament is polarised (+ve/-ve).
Rigid, long straight.

Question 11

Microtubules - Function (12) [2,1,4.2]

Answer 11

Intracellular transport
- Diiferent motors for different products being moved.
- Directionality of filament is vital.
Organises position of organelles
- Provides polarisation of cells.
Rhythmic beating of cillia and flagella
- Motile (capable of motion) processes with highly organised microtubule core.
- Core = 9 pairs of microtubules, around 2 central microtuule (axoneme).
- Bending of cillia and flagella is driven by the motor protein Dyenin.
- Basal body, at the base of the tubule, controls assembly of the axoneme.
Examples
- Cillia in airways, sweeping mucus and debris from lungs.
- Flagella on spermatozoa.

Question 12

Microtubules - Function (12) [2,1,4.2]

Answer 12

Intracellular transport
- Different motors for different products being moved.
- Directionality of filament is vital.
Organises position of organelles
- Provides polarisation of cells.
Rhythmic beating of cillia and flagella
- Motile (capable of motion) processes with highly organised microtubule core.
- Core = 9 pairs of microtubules, around 2 central microtuule (axoneme).
- Bending of cillia and flagella is driven by the motor protein Dyenin.
- Basal body, at the base of the tubule, controls assembly of the axoneme.
Examples
- Cillia in airways, sweeping mucus and debris from lungs.
- Flagella on spermatozoa.