Cytoskeleton And Cellular Architecture Pt. 2

Front 1

Of the three filaments, which is the least flexible?

Back 1

Microtubules

Front 2

What kind of energy does microtubule (MT) assembly require?

Back 2

GTP

Front 3

What does dynamic instability mean?

Back 3

The rapid switching between growth and shrinkage shown by microtubules. Occurs primarily at the positive end. Allows MTs to undergo rapid remodeling, and is crucial for their function.

Front 4

What is one of the primary functions of MTs?

Back 4

To move cargo through the cell (trafficking). This requires more energy (ATP).

Front 5

What is the MT organizing center?

Back 5

The centrosome. MTs radiating out from the centrosome support the plasma membrane. This contributes to the size and shape of the interphase cell. The network created is also what traffics cargo through the cell.

Front 6

Where is the centrosome located when the cell is in interphase?

Back 6

Typically close to the nucleus.

Front 7

What is the centrosome constructed of?

Back 7

A pair of centrioles surrounded by a matrix of proteins (called the pericentriolar material). This matrix contains hundreds of ring-shaped structures formed from a special tubulin called gamma tubulin.

Front 8

What does each gamma tubulin ring complex serve as?

Back 8

The starting point, or nucleation site, for the growth of one MT. The minus end of each MT is embedded here (the centrosome).

Front 9

What is the mitotic spindle?

Back 9

Occurs when the cell enters mitosis and MTs disassemble and reassemble into this intricate structure. Provides the machinery that will segregate chromosomes equally into the two daughter cells.

Front 10

What can be seen at the poles in mitotic cells?

Back 10

Spindle poles. MTs attached to spindle poles also attach to chromosomes to drive chromosome positioning and segregation during mitosis.

Front 11

What is the basal body?

Back 11

An organizing center for MTs that form cilia in ciliated cells. It anchors cilia to the plasma membrane. It also regulated the motion of the cilia.

Front 12

What are cilia?

Back 12

Hair like structures covered by plasma membrane. They extend from the surface of many kinds of eukaryotic cells. Each contains a core of stable MTs arranged in a bundle that grow from the basal body.

Front 13

The centrosome does not play a role in what?

Back 13

Segregating chromosomes during mitosis. This is the job of spindle fibers and spindle poles.

Front 14

What DOES the centrosome play a role in?

Back 14

Supporting large organelles such as the Golgi and Endoplasmic Reticulum, supporting the plasma membrane, and organizing microtubules.

Front 15

Describe the structure of MTs.

Back 15

Hollow tubes made up of globular tubulin subunits. This subunit is a heterodimer made up of an alpha tubulin and beta tubulin protein.

Front 16

How do the MT subunits stack together?

Back 16

Through noncovalent interactions.

Front 17

What is a protofilament, and how many create the tube structure of MTs?

Back 17

They are linear chains of alternating alpha and beta tubulin dimers that form the tube like structure. 13 parallel protofilamentd make up the MT tube structure.

Front 18

True or false: each protofilament has structural polarity, giving the MT a plus and a minus end.

Back 18

True

Front 19

What do both alpha and beta tubulin proteins bind to?

Back 19

GTP. This is what helps polymerize and depolymerize MTs. The two proteins also bind to each other in head to tail fashion.

Front 20

Describe the growing process of MTs.

Back 20

GTP-bound alpha/beta tubulin subunits are fundamental to MT growth. As long as the GTP on the filaments remains unhydrolyzed (creating a GTP cap), the MT will grow.

Front 21

Describe the shrinking process of MTs.

Back 21

GTP is hydrolyzed as the filament builds. Eventually, hydrolysis will catch up to the end of the MT, transforming the GTPs in the cap to GDP. This GDP-tubulin end is unstable, leading to disassembly of the MT.

When shrinking, the proto protofilaments peel away.

Front 22

What is catastrophe?

Back 22

The disassembly of an entire MT caused by GTP hydrolysis to GDP at the end of the MT because GDP-tubulin is unstable.

Front 23

True or false: the + end of an MT is unstable on its own and can't be stabilized.

Back 23

False. While it is unstable on its own, other proteins can stabilize it.

Front 24

What are the two typed of protein that regulate MT + end stability?

Back 24

1. MAPs (Microtubule associated proteins). Regulate length and stability.

2. TIPs (Microtubule tracking proteins). Mediate end dynamics and attachments

Front 25

What is an example of a MAP protein?

Back 25

Tau. Found in neurons. It binds to the side of the MT, but stabilizes the + end.

Front 26

Give an example of a disease caused by improper function of the MAP tau.

Back 26

Alzheimers. Tau fails to bind properly to neuron MTs. This causes the tau proteins to aggregate and form neurofibrilary tangles. Contributes to neurodegeneration.

Front 27

True or false: Cargo can only move away from the MT organizing center.

Back 27

False. Cargo can move toward or away from the MTOC.

Front 28

What are the two types of MT motor proteins?

Back 28

1. Dyneins (move cargo inward toward MT negative end).

2. Kinesins (primarily move cargo outward toward plus end of MT).

Front 29

What are the structures/mechanisms of dyneins and kinesins?

Back 29

They are similar in both. They have two head domains, two stalk domains that twist together to form a coiled coil, and two tail domains.

The head domains attach to the MT while the tail domains attach to the cargo (vesicles, organelles, other MTs).

Front 30

What kind of energy do motor proteins require?

Back 30

ATP hydrolysis.

Front 31

What is this an image of?

Back 31

A motor protein "walking" it's cargo along an MT. Think of the head domains as feet.

Front 32

What is this an image of?

Back 32

Green = MTs

Yellow = Centrosome

Front 33

What is this an image of?

Back 33

Green = MTs

Blue = DNA

Orange = Spindle Poles

Front 34

What is this an image of?

Back 34

TEM of a centrosome

Left: Light gray is the pericentriolar material. Dark gray/black are the centrioles.

Right: Hi magnification of short MT triplets in centriole.

Front 35

What is this an image of?

Back 35

A side view and cross section of an MT protofilament.

Front 36

What is this an image of?

Back 36

Green = MTs

Red = Basal Body

Front 37

What is this an image of?

Back 37

The 9+2 array that MTs form in cilia and flagella.

Front 38

What is this an image of?

Back 38

Cilia of a lung cell.

Front 39

What is this an image of?

Back 39

Flagella of sperm cells.

Front 40

What is this an image of?

Back 40

Green: Plectin

Cyan: IFs

Red: MTs

SEM image.

Front 41

What is this an image of?

Back 41

A kinesin motor protein.

Front 42

What is this an image of?

Back 42

Red: MAPs (MT-associated protein)

Green: TIPs (MT tracking protein)

Front 43

What is the standard structure of cilia and flagella?

Back 43

9 doublets of MTs surrounding 2 single MTs. Called the 9+2 array.

Front 44

What motions does dynein cause in isolated doublet MTs? In a normal flagella?

Back 44

1. The MTs slide passed each other.

2. Linking proteins hold MTs together so they won't slide. Instead they bend.

Front 45

What is the 1⁰ cilium? What cells have it?

Back 45

The primary cilium is non-motile and functions in signaling. Most cells lack beating cilia but have this instead.