Lecture 18 - The Cytoskeleton & CM: Muscles

Question 1

def: responsible for the movement of biomolecules and other cellular components over long distances

Answer 1

microtubules

Question 2

at the ends of MT, cargo switch over to __________ for local movements

Answer 2

microfilaments

Question 3

what are the functions of a myosin motor protein?

Answer 3

• muscle contraction
• cell movement
• phagocytosis
• vesicle transport

Question 4

most myosin motors move toward the (+) end, but _______ is an exception

Answer 4

myosin VI

Question 5

what does the globular head of myosin bind?

Answer 5

actin and uses ATP hydrolysis to move along the filament

Question 6

myosin move along ____

Answer 6

MF

Question 7

which can take bigger steps, kinesin or myosin V?

Answer 7

• myosin = 36 nm
• kinesin = 8nm

Question 8

def: can form bipolar filaments, are important for muscle contraction, cytokinesis, cell migration, and focal adhesions, with 2 heavy chains

Answer 8

Type II myosins

Question 9

myofibrils are subdivided along their length into repeating units called __________

Answer 9

sarcomere

Question 10

sarcomeres are comprised of :

Answer 10

• thick, myosin II - bipolar filaments
• thin, actin microfilaments

Question 11

def: staggered arrays if myosin II

Answer 11

thick filaments

Question 12

def: actin microfilaments with other bound proteins

Answer 12

thin filaments

Question 13

def: long, rod-like molecule that fits in grooves along the sides of the F-actin helix

Answer 13

tropomyosin

Question 14

def: comprised of three polypeptides: TnT, TnC, and TnI

Answer 14

troponin

Question 15

what is the ratio of troponin and tropomyosin associating with each other?

Answer 15

1:1

Question 16

def: caps the (-) ends of the filaments to maintain stability

Answer 16

tropomodulin

Question 17

def: caps the (+) ends and attaches the microfilament to the Z line

Answer 17

CapZ

Question 18

def: stabilizes and bins the thin filament to the Z line

Answer 18

nebulin

Question 19

def: cross-links the Z line to the microfilament, keeping the thin filaments in parallel arrays

Answer 19

alpha-actinin

Question 20

def: bundles the myosin molecules

Answer 20

myomesin

Question 21

def: attaches the thick filaments to the Z lines and keeps thick filaments correct position relative to think filaments during contraction

Answer 21

titin

Question 22

how are cross bridges formed ?

Answer 22

by interactions between the actin-binding domains of myosins in the thick filament and the F-actin of the thin filaments

Question 23

what is opened when muscle cells receive nerve impulses at the neuromuscular junction?

Answer 23

ryanodine receptor, which triggers release of Ca2+ into sarcoplasmic reticulum

Question 24

when does muscle contraction stoP?

Answer 24

when Ca2+ is actively transported back into the sarcoplasmic reticulum

Question 25

what does calcium binding to TnC do?

Answer 25

changes the conformation of troponin, pulling tropomyosin off the myosin binding site

Question 26

def: thin sheet of cytoplasm

Answer 26

lamellipodium

Question 27

def: thin pointed protrusion

Answer 27

filopodium

Question 28

what happens in lamellipodia?

Answer 28

loose networks of actin form a dendritic network pushing on the membrane

Question 29

def: complex of actin-related proteins that nucleate new branches on the sides of filaments

Answer 29

Arp2/3 complex

Question 30

def: directional movement in response to a graded chemical stimulus

Answer 30

chemotaxis

Question 31

def: occurs through the formation of protrusions predominantly on one side of a cell

Answer 31

directional migration

Question 32

def: cells move toward a higher concentration of the diffusible molecules

Answer 32

chemoattractants

Question 33

def: cells move toward a lower concentration of the diffusible molecules

Answer 33

chemorepellents