Cell motility

Question 1

What does cell motility require?

Answer 1

• energy
• guidance
• mechanical interaction with something out the cell
• swimming vs crawling
• microtubules vs actin microfilaments

Question 2

Describe what is required for cells to swim?

Answer 2

microtubules

Question 3

Describe what is required for cells to swim?

Answer 3

actin microfilaments

Question 4

What are microtubules composed off?

Answer 4

hollow tubes of a & b tubulin (they alternate)
- 13 protofilaments
- has intrinsic polarity due to the 2 tubulin subunits

Question 5

What is the structure of microtubule-based motility?

Answer 5

Cilia & Flagella

Question 6

Where is flagella used in cells?

Answer 6

sperm/ protozoa

Question 7

Where is cilia used in cells?

Answer 7

respiratory tract/reproductive tract

Question 8

What is the difference between cilia & flagella?

Answer 8

they have the same structure, but they have different lengths:
cilia - 2-10 x 0.25um
flagella - 100-200 x 0.25um

Question 9

What is larger - cilia or flagella?

Answer 9

flagella (10 times larger)

Question 10

What is the major functional structure of the cilia & flagella?

Answer 10

Axoneme

Question 11

What is the microtubular arrangement of the axoneme?

Answer 11

9+2 microtubule assembly

Question 12

Describe the 9+2 microtubule assembly composition

Answer 12

• 9 outer doublets
• Radial spokes
• Inner pair

Question 13

How many protofilaments do complete (A) fibres have?

Answer 13

13 protofilaments

Question 14

How many protofilaments do incomplete (B) fibres have?

Answer 14

10

Question 15

What is dynein arms?

Answer 15

the motor protein in microtubules

Question 16

What links the 2 central doublets?

Answer 16

Dynein - the presence of ATP allows sliding of microtubules (in separate directions)

Question 17

What are the 2 dynein arm-dependent functions?

Answer 17

Inner arm - waveform
Outer arm - power

Question 18

What is the transition zone?

Answer 18

where flagella/cilia meets the plasma membrane

Question 19

What is the function of basal bodies?

Answer 19

cell motility

Question 20

What happen if actin acts on a muscle?

Answer 20

moves organism

Question 21

What happen if actin acts on a non-muscle?

Answer 21

moves cells/tissues

Question 22

Does an actin monomer have polarity?

Answer 22

Yes

Question 23

What is in the middle of an actin subunit?

Answer 23

bound nucleotide (ATP)

Question 24

What can occur to the ATP molecule in the middle of a G actin filament?

Answer 24

It can be hydrolysed released energy and leaving ADP

Question 25

What can occur to the GTP in microtubules?

Answer 25

can be converted to GDP

Question 26

What is actin treadmilling?

Answer 26

addition of actin at one end, while removing at the other end also occurs.

Question 27

What is larger - an actin filament or microtubule?

Answer 27

Microtubule

Question 28

What is the difference in the nucleotide in actin vs microtubule?

Answer 28

Actin - ATP
Microtubule - GTP

Question 29

What does profilin (actin-binding protein) inhibit?

Answer 29

profilin inhibits nucleation

Question 29

What regulates actin dynamics?

Answer 29

Accessory proteins

Question 29

What does profilin bind to?

Answer 29

ATP actin

Question 30

Describe how actin-based motility works?

Answer 30

Filopodium - narrow projections

Lamellipodium - broader projections of membrane

Stress fibres - quite static - transmit force & allow cell to be contractile

Cortical actin ring - around edge of cell