Cytoskeleton II - IV

Microtubules

built from tubulin

tubulin

a dimer composed of two globular proteins called:

• a tubulin

• b tubulin

a and b tubulin

Tubulin dimers contain:

a.) Actin + myosin

b.) a and b tubulin

c.) DNA + RNA

d.) DNA only

noncovalent

a and b tubulins are attached to each other with a _______ bond and form a linear chain of tubulin dimers.

Microtubules

hollow structures made of 13 dimers of α-tubulin and β-tubulin

Centrosome

consists of a pair of centrioles surrounded by gel matrix proteins

g-tubulin

what special tubulin is inside the gel matrix proteins?

• serve a nucleation site

T

T or F?

Plants lack centrioles and have structures called the cell cortex instead.

dynamic instability

Microtubules continuously grow and shrink over time. What’s this process called?

microtubule

Each _______ behaves independently, not synchronized with neighbors.

elongate; depolymerize

The centrosome-anchored array is constantly reorganizing because some microtubulues _______ while others ________.

GTP-bound

Which tubulin?

add to the plus end for microtubule growth

GTP cap

Forms at the growing end and stabilizes the microtubule to allow for continued elongation

GDP

GTP hydrolyzed into ____ leads to loss of GTP cap.

GTP cap

Loss of ____ _____ results in rapid microtubule shrinkage.

polarity

Microtubules are “permanently” structured based on their _____.

Microtubule associated proteins

binding partners

• help stabilize microtubules against:

  • disassembly

  • promote nucleation

Motor proteins

move along the cytoplasmic microtubules

• belong to a family of two proteins:

  • kinesins and dyneins

motor proteins

Most have:

• two globular (ATP-binding) heads (attach to microtubule)

• single tail (attach to cargo: organelle or vesicle)

Tubulin

Microtubules are made of:

a.) Actin

b.) Tubulin

c.) Keratin

d.) Myosin

Centrosome

The microtubule-organizing center is the:

a.) Golgi

b.) Centrosome

c.) Ribosome

d.) Lysosome

GTP cap

What stabilizes a growing microtubule?

a.) ATP cap

b.) GTP cap

c.) ADP cap

d.) GDP cap

Kinesin

Which motor protein moves toward the plus end?
a.) Dynein

b.) Kinesin

c.) Myosin

d.) Actin

9+2

Cilia and flagella have what structure?

a.) 8+2

b.) 9+2

c.) 10+2

d.) 7+3

Flagella

• longer

• move the entire cell

• used to propel sperm and many protozoa

Cilia

• shorter

• beat in a whiplike fashion to move fluid over the surface of the cell or to propel single cells through a fluid

T

T or F?

Both cilia and flagella have a similar internal structure.

both

Cilia, flagella, or both?

contain stable microtubules moved by dynein.

both

Cilia, flagella, or both?

Cells use such stable microtubules as stiff polarized structures for movement.

ATP; hydrolysis

Motor binding protein movement is powered by _____ binding and ______, which drive conformational changes in the protein.

ATP hydrolysis

Motor binding protein movement:

___ _____ at the rear head weakens its attachment, allowing it to detach from the microtubule.

ADP; ATP

_____ release and _____ binding at the front head trigger a conformational shift that swings the rear head forward, completing one step.

dynein

The movement of _____ causes the flagellum/cilium to bend.