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Flashcards in Muscle contraction Deck (55):
1

Where does actins contractile properties come from?

interaction with its motor protein myosin

2

What is cell contraction involved in?

Cell crawling - pulling the tail end of the cell forward

3

When does the contractile filaments form form the cleavage furrow?

During cytokinesis

4

What does myosin move along for movement?

actin filaments

5

What provides the energy for myosin movement along actin filaments?

myosin hydrolyze ATP

6

What does Myosin function like?

dynein and kinesin that move along MTs

7

In which direction does all of myosin move?

toward the plus end (like kinesin)

8

How many different myosins are there?

14 different kinds of myosin

9

What does all myosin share?

homology in their amino acid sequence
they differ mostly in their C -terminus tail
some in their N terminus tail

10

Which eukaryotic cells are myosin most common to?

all/most eukaryotic cells (protozoa, plants, animals) some are taxon specific

11

What does myosin function as?

a dimer
three as a monomer

12

What are the the myosin families that function as a monomer?

Myosin I
Myosin II

13

What are the domains of the Myosin I family?

one head ATPase domain
one tail cargo binding domain

14

What is the function of the head domain on the myosin I family?

interacts w/ actin filaments (factin binding domain)
hydrolyze ATP - allows it to walk along the actin filament

15

What is the function of the tail domain in myosin I family?

interacts with components
is specific to cargo

16

What is various myosin I proteins?

C - terminus that bind different cargo

17

Where are myosin II proteins most abundant in?

Skeletal muscle
can be found in non muscle cells

18

What do Myosin II dimers cluster to form at their tail domain in skeletal muscle?

thick myosin filament
common in muscle cells

19

What does the myosin monomers and dimers show?

structural polarity

20

Why are myosin monomer and dimers bipolar?

one set of heads binds actin filaments pilling them in one direction
another set of heads binds to another set of actin filaments and pulls the opposite direction

21

What is the overall effect on actin of opposite binding heads of myosin?

slide sets of oppositely oriented actin filaments past one another - generation of overall contractile force

22

What are skeletal muscle formed from?

parallel arrangements of multiple muscle fibers

23

What is a single skeletal muscle cell equal to?

muscle fiber

24

how does a muscle fiber run?

whole length of a muscle

25

How long are muscle fibers?

cm long
50 m in diameter

26

How are muscle fibers formed?

from fusion of many precursor cells

27

Why are muscle fibers multi nucleated?

because the precursor cells retain their nucleus

28

What is a sacrolemma?

plasma membrane of a muscle fiber

29

What are T- tubules?

in sacrolemma they are deep invaginations into the center of the fiber

30

What are myofibrils?

contractile elements of muscle fiber

31

What is each muscle fiber compose of?

multiple myofibrils that run along the long axis of the muscle

32

How long are myofibrils?

sometimes long as the muscle fiber itself
1-2m in diameter

33

What are sacromeres?

individual unit that make up myofibrils

34

How long are sacromeres?

2.5-3 m long

35

how many sacromeres in series is in a muscle 30 cm long?

10,000 sacromeres in series
3 * 10000 = 30000 = 30 cm

36

What gives the cardiac and skeletal muscle its striated appearance?

the repeating structure of sacromeres

37

What are sacromeres compose of?

actin
myosin
associated proteins

38

What is the thin fibers in sacromeres?

actin filaments

39

What does the plus end of actin filaments interact with?

Z disc

40

where does each minus end of actin filaments orient?

toward the center of the sacromere, overlaps with myosin filaments

41

What are the thick filaments in sacromeres?

bipolar clusters of Myosin II

42

What is the position of thick filaments (myosin II) in sacromeres?

centrally positioned in each sacromere

43

What is the M- line

mid point of thick filament where myosin head begin being arranged in the opposite direction

44

What is the Z-disc?

point of attachment of actin filaments

45

What is the Z- disc built of?

CapZ
actinin

46

How does the plus end of actin filaments attach to Z-line?

actin binding protein CapZ
prevents depolymerization of plus end and holds them in a regularly spaced arrangement

47

What is nebulin?

actin side binding protein that determines length of actin filaments

48

What is the minus end of capped of with?

tropomudulin

49

What is titian?

side binding protein for myosin (determines length of thick filament)
act as a molecular spring to help bring sacromers back to its appropriate length after to much stretch

50

Where does titin stretches from?

the Z disc into thick filament, where it interacts with the myosin tails and up to the M-line
(there are two titin ends from Z disc to Z disc)

51

how are sacromeres viewed using polarized light microscopy?

display a characteristic pattern of light and dark regions

52

What is the I-band?

light band

53

What does the I-band span?

technically spans two sacromeres but w/in sacromeres runs Z-line to outer edge of thick myosin filaments
thin act filaments only (no overlap with myosin)

54

What is the A band?

dark band
darker staining region in the middle of the sacromere
may overlap with actin filaments towards either end

55

What is the H band?

helles
lighter staining region in the middle of the sacromeres
myosin only no actin overlapping with myosin filament s

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