Lecture 2

Question 1

IClicker Question:

What are the 3 components of phenotype of an adult organism?

Answer 1

Physiology, Morphology & Behaviour

Question 2

IClicker Question:

Does physiology influence evolutionary changes over time?

Answer 2

Yes

Question 3

How do animal cells generate movement?

Answer 3

Cytoskeleton & Motor proteins

Question 4

What is a cytoskeleton?

Answer 4

The cytoskeleton is like a cell’s internal framework or “skeleton”. It is made up of protein fibers that help give the cell its shape, support and structure. It also works like a system of tracks that helps move things around inside the cell and is involved in cell movement

Question 5

What is a motor protein?

Answer 5

A motor protein is a special protein in cells that moves things by “walking” along the cytoskeleton using energy from ATP. It helps transport molecules, like vesicles, within the cell and plays a key role in cell movement.

Question 6

What are the four general types of cellular movement?

Answer 6

1.) Polymerization
2.) Mobile cytoskeleton
3.) Mobile motor
4.) Mobile motor & cytoskeleton

Question 7

What are the charcteristics that define the type of cellular movement?

Answer 7

The type of cellular movement depends on if the cytoskleton, the motor protein, or both can move.

Question 8

What is polymerization?

Answer 8

Polymerization is the reorganization of the cytoskeletal network - growth of the cytoskeleton in one region of the cell pushes the cell membrane outward - used in amoeboid movement

Question 9

What is Mobile Cytoskeleton?

Answer 9

Motor proteins attached to the cell membrane pull on the cytoskeleton, moving an element of cytoskeleton. *Ratcheting action of motor proteins pull the cytoskeleton in one direction

Question 10

What is Mobile Motor?

Answer 10

Motor proteins “walk” along relatively fixed elements of the cytoskeleton - can be used to transport cargo throughout cell.

Question 11

Mobile Motor and Cytoskeleton

Answer 11

Motor proteins and cytoskeleton are arranged in arrays that they slide over each other, pulling the cell into a different shape. When motor proteins are activated, the cytoskeletal elements slide over each other to cause a change in cell shape

Question 12

What are the 3 different types of fibers within Cytoskeleton?

Answer 12

1.) Microtubules
2.) Microfilaments / Actin Filaments
3.) Intermediate Filaments

Question 13

What are microtubules?

Answer 13

Microtubules are long hollow tubes composed of repeating units of tubulin.

Question 14

What is a tublin?

Answer 14

Tubulin is a dimer of α-tubulin and β-tubulin

Question 15

Do microtubules have polarity? (Positive & Negative end)

Answer 15

Yes

Question 16

What are the factors that influence the rate of growth and the rate of shrinkage of microtubules?

Answer 16

1.) Concentration of tubulin
2.) Whether or not the GTP bound by β-tublin is hydrolyzed
3.) Microtubule associated proteins (MAPS)
4.) Temperature

Question 17

What does critical concentration mean in terms of Microtubules?

Answer 17

Critical concentration → The concentration at which microtrubules are in a dynamic equilibrium where they neither grow or shrink.

Question 18

What happens to the microtubules above the critical condition?

Answer 18

Microtubules will grow (polymerize), as there are enough free tubulin dimers available to be added to the ends of the microtubule.

Question 19

What happens to the microtubules below the critical condition?

Answer 19

Microtubules will shrink (depolymerize), as there are not enough free tubulin dimers available to replace those lost from the ends of the microtubule.

Question 20

Does both ends of microtubules grow and shrink at the same rate?

Answer 20

Theplus (+) end(the rapidly growing end) has alower critical concentration, meaning tubulin is more likely to be added here compared to the minus end.

Theminus (−) endhas ahigher critical concentration, meaning it is more likely to lose tubulin subunits unless the free tubulin concentration is higher.

Question 21

What is a MTOC?

Answer 21

Microtubule Organizing Center

Question 22

Where is the MTOC located within a cell?

Answer 22

In most cells, MTOC is located near the nucleus

Question 23

Is there polarity in MTOC?

Answer 23

Typically, the minus end of each microtubule is located at the MTOC while the (+) end extends out toward the cell membrane

Question 24

What motor proteins work with microtubules?

Answer 24

Kinesin & Dynein

Question 25

Which direction does Kinesin move towards?

Answer 25

Towards the positive end

Question 26

Which direction does Dynein move towards?

Answer 26

Towards the negative end

Question 27

The Chemotherapy Drug - Taxol

First isolated from the bark of Pacific Yew tree (Taxus brevifolia)
Now produced from cell culture of Pacific Yew
Used to treat solid cancer tumours (e.g. ovarian, bladder, lung, etc.)

1.) Which cytoskeleton element is targeted?
2.) Which cellular process is targeted?

Answer 27

1.) Microtubules
2.) Mitosis / Cell division