ch 17

Question 1

actin filaments

Answer 1

• made of actin monomers
• provide support to the cell
• flexible
• smallest

Question 2

what makes up intermediate filaments? what do they do?

Answer 2

• made up of fibrous intermediate filament proteins
• form a strong, durable network in the cytoplasm of the cell
• long twisted strands of protein

Question 3

what are the 4 kinds of intermediate filaments and where are they found

Answer 3

found in cytoplasm
- keratin filaments (epithelial cells)
- vimentin filaments (connective tissue cells, muscle cells, glial cells)
- neurofilaments (all nerve cells)
nuclear
- nuclear lamins (all animal cells)

Question 4

how are intermediate filaments formed

Answer 4

2 monomers = dimer
2 dimers = tetramer
2 tetramers = octamer

Question 5

what make up microtubules? what do they do?

Answer 5

• made up of tubulin dimers
• help position organelles in eukaryotic cells
• biggest
• most rigid

Question 6

Describe two congenital diseases that result from defects in intermediate filament. Be sure to explain which type of intermediate filaments are involved and their function in normal cells

Answer 6

Progeria: defects in nuclear lamin causes premature aging; lamin A is assembled into a uniform nuclear lamina in a normal cell
Epidermolysis bullosa: skin is highly vulnerable to mechanical injury; keratin provides tensile strength to epithelial cells in normal cells

Question 7

what aids in the bundling of intermediate filaments and links these filaments to other cytoskeletal protein networks

Answer 7

plectin (linker protein)

Question 8

Explain why drugs that interfere with microtubule function are often very effective anti-cancer drugs

Answer 8

The inactivation of the mitotic spindle eventually kills dividing cells. Because cancer cells divide in a less controlled way than normal cells, they can be destroyed by drugs that either stabilize or destabilize microtubules.

Question 9

Describe how kinesin and dynein are able to move cargo along microtubules

Answer 9

Their globular heads are enzymes with ATP-hydrolyzing activity, this reaction provides the energy for driving a directed series of conformational changes in the head that enable the motor protein to move along the microtubule.

Question 10

Compare and contrast the structure of actin microfilaments with microtubules

Answer 10

actin filaments are thinner twisted chains of actin monomers while microtubules are hollow tubes made of globular tubulin subunits. both have a plus (where globular tubulin or an actin monomer is added) and minus end

Question 11

Explain how myosin-I moves cargo along actin microfilaments

Answer 11

The head domain of the myson-I binds to the actin filament and has ATP-hydrolyzing motor activity that enables it to move along the filament.

Question 12

Draw a cross section of a eukaryotic cilium indicating the position of all microtubules involved. You do not have to draw dynein arms or any non-tubulin based cross-linking structures. Just the microtubules.

Answer 12

9-2

Question 13

what is shown here

Answer 13

microtubules can be stabilized by attachment to capping proteins

Question 14

how does gtp hydrolysis control the dynamic instability of microtubules

Answer 14