Cell bio 4: Cell Motility

Which two components of the cytoskeleton are involved in cell motility and which is not?

Microtubules and microfilaments are involved, intermediate filaments are not

What is the motor protein associated with F-actin?

Myosin

What are the motor proteins associated with microtubules?

Kinesin and dynein

How large is one ‘step‘ of a motor protein?

8nm

How many ‘steps’ does a motor protein take each second?

40

In what direction does kinesin travel and along what filament?

Microtubules, from - end to + end (from MTOC to cell periphery)

In what direction do dyneins travel and along what filament?

Microtubules, from + to - (from periphery to MTOC)

In what directions do most myosins travel and along what filament?

Actin, from - to +

In what directions does myosin VI travel and along what filament?

Actin, from + to -

Describe one example of one way polymerisation of actin filaments can be used in a cell to generate force

Listeria is a bacterium that gives you food poisoning. It gets taken up into the cytoplasm of the gut cell and once inside ActA, an actin nucleating protein, stimulates actin to polymerise and form comet tails of actin filaments. The actin is human actin not the bacterium’s own actin. This allows the bacteria to infect neighbouring cells.

In a sarcomere, to which disc (A-Z) are all filaments anchored?

Z disc

How many different classes of myosin are there?

At least 15

Which number myosin (1-15) is ‘conventional‘ myosin?

II

What does myosin V do?

Organelle motor actin used typically for short-range movements vs microtubule motors

What makes myosin VI unusual?

It travels in the opposite direction to most myosins

Which sensory process are myosin VI and VII involved in?

Hearing

Describe crawling cell locomotion

Polymerisation coupled with adhesion causes the cell to move forward. Actin formation creates lamellipodia, adhesion formation, actin-myosin contraction causes tail to retract.

What is a lamella

The flattened portion of the nucleus in crawling cell locomotion

How do cilia and flagella differ in size?

Flagella (60 micrometres) are about 10x bigger than cilia (6 micrometres)

What is an axoneme?

The core of a cilium or flagellum, composed of microtubules

Describe the arrangement of microtubules in an axoneme

9+2 arrangement of 9 doublet microtubules and one central pair

The action of which motor protein causes sliding action between adjacent doublets?

Dynein

How does the movement of the axoneme differ in cilia and flagella?

In flagella the axoneme creates a whipping motion, whereas in cilia the axoneme twists in an oscillating wave

What is the general name of diseases linked to cilia?

Ciliopathies

What is the longest nerve to exist?

The recurrent laryngeal nerve, which controls the larynx

Where is most myosin II found (lamellipodium, filopodium or stress fibres)?

Stress fibres