Block 1 Lecture 7

Question 1

what are the 3 protein filaments in the cytoskeleton

Answer 1

1. microfilaments
2. intermediate filaments
3. microtubules

Question 2

what are the functions of the cytoskeleton

Answer 2

• maintains cell shape
• provides strength
• locomotion
• chromosome separation
• intracellular transport of organelles

Question 3

what is the function of microfilaments

Answer 3

• connect organelles to membranes
• influence cell motility and shape
• form a band beneath plasma membrane

Question 4

what is the function of intermediate filaments

Answer 4

structural stability

Question 5

what is the function of microtubules

Answer 5

influence cell structure and shape, motility-organelle movement-cilia and flagella, provide tracks for motor proteins

Question 6

how thick are microfilaments

Answer 6

6-8 nm

Question 7

how thick are intermediate filaments

Answer 7

10 nm

Question 8

what are in intermediate filaments

Answer 8

keratins, nuclear lamina, neurofilaments, vimentins

Question 9

where are keratins found

Answer 9

epithelial cell

Question 10

what do nuclear lamina do

Answer 10

stabilize the inner membrane of the nuclear envelope

Question 11

what do neurofilaments do

Answer 11

strengthen long axons of neurons

Question 12

what do vimentins do

Answer 12

provide mechanical strength to muscle cells

Question 13

how thick are microtubules

Answer 13

25 nm

Question 14

what is the plus end? minus end?

Answer 14

plus end= growing end

minus end=shrinking end

Question 15

how do microtubules shrink

Answer 15

release of tubulin dimer (depolymerization)

Question 16

how do microtubules grow

Answer 16

polymerization of tubulin dimers

Question 17

what is a centrosome

Answer 17

orthogonal arrangement of two centrioles

Question 18

what is a centriole

Answer 18

barrel shaped microtubule structure

Question 19

what are the 2 microtubules motors

Answer 19

-kinesins and dyneins

Question 20

what do kinesins do

Answer 20

move toward (+) end away from nucleus (anterograde)

Question 21

what do dyneins do

Answer 21

move toward (-) end towards nucleus (retrograde)

Question 22

what is anterograde

Answer 22

movement towards synapse

Question 23

what is retrograde

Answer 23

movement towards cell body

Question 24

what is the speed, purpose, and mechanism of fast axonal transport?

Answer 24

speed = 100-400 mm/day
purpose= anterograde movement to transport organelles and vesicles containing membrane proteins to nerve terminal. retrograde movement to transport vesicles containing neurotrophic factors back to cell body
mechanism  = motor proteins running along microtubules tracks

Question 25

what is the speed, purpose, and mechanism of slow axonal transport?

Answer 25

``` speed = 1-4 mm/day purpose = delivers cytosolic and cytoskeletal proteins to the nerve terminal mechanism = still being studied ```

Question 26

what do motor proteins do

Answer 26

- stepwise | - move unidirectionally

Question 27

what are the steps of motor proteins

Answer 27

1. ATP binding to motor 2. hydrolysis of ATP 3. release of ADP and Pi 4. binding of new ATP