Bevington 3

Question 1

Cytoskeleton function in eukaryotes

Answer 1

Maintaining cell shape
Positioning of organelles
Movement of vesicles
Cell motility
Cell division

Question 2

Main components in cytoskeleton (and key proteins)?

Answer 2

Microfilaments (actin proteins)
Microtubules (tubulin proteins)
Intermediate filaments (keratin proteins)

Question 3

Actin microfilament structure + function?

Answer 3

G-actin subunits comprise F-actin polymers
- Resist tension on cell
- Transport of membrane packaged material (vesicles)
- Localised cell contractions (Cleavage furrows
Amoeboid movement)

Question 4

Myosin motor protein mechanism? Examples of use

Answer 4

Hydrolysed ATP provides energy for myosin to ‘pull together’ actin filaments, ‘walking’ towards positive end of actin (where subunits are added)
- Actomyosin contractile protein complexes the basic of muscle contraction
- Amoeboid + leukocyte movement
-

Question 5

Tubulin microtubules - structure and function

Answer 5

Hollow tubes of tubulin dimers (alpha and beta tubulin)
- Moved by kinesin and dynein motor proteins
- easily assembled/disassembled
Function
- compression resisting (supports cell structure)
- movement of vesicles
- Cell division in mitosis and meiosis

Question 6

Direction of movement
Kinesins
Dyneins
Myosin

Answer 6

K - plus
D - minus
M - plus

Question 7

Differences between

• Cillia
• Bacterial flagella
• Eukaryotic flaggela

Answer 7

Cillia - Contain microtubules, fluid circulation (e.g of mucus)
Bacterial - Contain flagellin, perform cell movement
Eukaryotic - Contain microtubules, perform cell movement

Question 8

Intermediate filaments, structure and function?

Answer 8

Fibrils made from keratin supercoiled together
- form cage like networks
- do not readily disassemble
- mechanically tough, apparent in skin, hair nails etc
Intracellular function
- Resist tension
- Maintain cell shape
- Fix position of nucleus and organelles
- Form nuclear lamellae