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MSKI Final Exam material > Dr. Seidler's Lectures on Contractile fibers > Flashcards

Dr. Seidler's Lectures on Contractile fibers Flashcards

1
Q

Myosin is composed of

A

coiled coil of two alpha helices:
2 heavy chains and 4 light chains

N terminus, hinge region, and a minus end

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2
Q

bipolarity

A

N terminus/hinge region—-minus end

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3
Q

what pars of the myosin coiled coil’s associate?

A

the minus ends to form the bare zone

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4
Q

There are ____ heads, ____ chains, and one ____ domain in myosin

A

2 N terminus heads (globular)
2 heavy chains, 4 light chains
rod domain (helical)

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5
Q

Where does myosin self-assembly?

A

at the tails

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6
Q

Muscle tissue is “in register”: what does that mean?

A

the striations line up together to form larger striations

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7
Q

how many thin filaments surround a thick filament

A

6

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8
Q

what anchors the thin filament?

A

the Z disc, “anchored” to Z disc

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9
Q

There is a ____ degree of rotational symmetry of the thin filament around the thick filament

A

60 degrees

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10
Q

what gives the thick filaments the ability to stack AND move around?

A

the linker protein

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11
Q

myosin has _____ amino acids per turn

A

3.5

so there are 7 amino acids per 360 degrees?
7

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12
Q

What kind of amino acid would we expect to find in the interior of the myosin?

A

hydrophobic

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13
Q

rigor mortis

A

respiration doesnt occur, so oxidative phosphorylation isn’t occurring, so the thin filaments aren’t being dragged along by the head groups (the myosin needs the ATP): the myosin remains attached (does not dissociate)

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14
Q

what kind of disease leads to a point mutation in the code for myosin?

A

a dominant

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15
Q

how many possibe binding partners does an actin (thin) filament have?

A

4

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16
Q

Tropomodulin

A

caps the minus end of the thin filament (not the Z disc)

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17
Q

CapZ

A

b-actinin, a heterodimner which associates with a-actinin, caps at the plus end

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18
Q

Troponin complex

A

Troponin T, I, C

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19
Q

Troponin T

A

binds tropomyosin and positions the complex on the filament

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20
Q

Troponin I

A

binds actin, inhibits myosin binding

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21
Q

Troponin C

A

binds Ca, relieves inhibition

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22
Q

Tn-I

A

inhibitory troponin: has three isoforms found in tissues.

cTn-I is found in cardiac tissue and its serum levels rise after a myocardial infacrtion

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23
Q

cTn-I

A

the isoform of inhibitory troponin that appears in serum after an infarction

24
Q

what method helps distinguish a myocardial infarction in the lab

A

an ELISA looking for cTn-I

25
Q

TIC

A

three small troponin proteins that transduce the role of calcium in muscle contraction

26
Q

what initiations contraction? ATP or Calcium?

A

Calcium

27
Q

What troponin does calcium bind to?

A

troponin C

28
Q

What actin monomer is in the assembled state?

A

G actin

29
Q

What actin monomer is in the depolymerized state?

A

F actin

30
Q

Pointed End

A

the end fixed to the Z disc

31
Q

the barbed end

A

hanging in space

32
Q

what are the proteins that make up the thin filaments?

A

actin, tropomysoin, regular intervals of the troponin complex

33
Q

alpha-actinin =

A

make up proteins that arrange the actin monomers in the hexagonal arrangement

these are within the actin bundles of myofibrils

34
Q

actins are held together at the Z discs by

A

alpha actinin

35
Q

the myofibrils are held together by

A

desmin

36
Q

Returning to the question of the myofibrils held in register, what does this?

A

the Z discs are all aligned two ways: a) the a-actinin anchors the actin at the designated point (the Z disc); these areas are then linked together by DESMIN

these then tether to costameres: these are tethering proteins to the sarcolemma

37
Q

costamere protein

A

dystrophen, tethers the myofibrils to the sarcolemma

38
Q

Titan

A

Sarcomere ruler

“molecular ruler”

BALANCES forces across the sarcomere. passive elasticity
muscle signaling

allows for elasticity without ripping

39
Q

DHP channel

A

it’s responsive to the action potential, but it’s mechanically
DHP is voltage dependent that is mechanically gated: it opens (mechanically) the ryanodine receptor.

40
Q

Hypocalcemic does what?

A

releases inhibition of the sodium channel and causes it to spontaneously fire

results in tetany

41
Q

Myosin light chain kinases

A

smooth muscle lacks troponin complexes, so these proteins are activated by calmodulin (Ca activated): MLCK then phosphorylated myosin light chain, enabling a myosin crossbridge to bind to the actin filament and permit contraction

42
Q

Calmodulin-MLCK

A

the main pathway for smooth muscle contraction

43
Q

Duchenne muscular dystrophy

A

X linked, reessive disorder with an incidence of 1/3500 boys

progressive muscle wasting

result from mutations in dystrophen gene (costamere)

44
Q

GSD V/McArdle disease

A

deficiency in muscle glycogen phosphorylase

autosomal recessive disease

deficiency in glycogen phosphorylase, rate limiting enzyme of glycogen degradation

cleaves glucose residues from glycogen for release as glucose-1 phosphate.

marked by myoglobin in the urine during intense exercise

individuals suffer immense fatigue because they can’t get glucose

45
Q

GSD VI

A

mutations in chromosomes 14/11 cause mutations of phosphorylase = Hers Disease in the liver

46
Q

GSD V versus GSD VI

A

GSD VI occurs in the liver.

GSD V is activated by AMP, Ca-Calmod, and G actin.
GSD VI is inactivated by glucose and no affected by AMP

both forms are activated by phosphorylation catalyzed by PhK

47
Q

Duchene

A

no dystrophin

48
Q

Beckers

A

truncated dystrophin

49
Q

what does dystrophin do?

A

tether’s outer bundles of myofibrils to surface membrane

50
Q

dystrophen is in the

A

carsomeres: helps withstand strenuous exercise

51
Q

what happens if you didn’t have dystrophin?

A

your muscles would rip

52
Q

What mediates the glycogen to glucose degradation in the liver?

A

glycogen phosphorylase

53
Q

What mediates glucose-6-phosphate breakdown to pyruvate in the liver?

A

Glucose-6-Phosphatase

54
Q

Glycogen Phosphorylase is activated by

A

AMP signaling

55
Q

AMP binds to what site on Glycogen phosphorylase?

A

the “s” catalytic subunit (it’s the allosteric, not active site)

56
Q

How is glycogen phosphorylase activated?

A

AMP bings to an allosteric site and a phosphorylase P’s a serine residue, increasing its activity

57
Q

phosphorylase kinase

A

activated by calmodulin, it then activates glycogen phosphorylase

MSKI Final Exam material (15 decks)

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