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BioChem Exam 3 > Muscles & Motility > Flashcards

Muscles & Motility Flashcards

1
Q

Muscle is composed of?

A

Actin/myosin

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2
Q

Types of energy used by muscle?

A

ATP
Ca
Creatine phosphate

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3
Q

Structures such as cilia, flagella, centrioles, basal bodies, centromeres, mitotic spindles are made of?

A

Microtubules with tubulin, dynein, kinesin

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4
Q

Intermediate filaments?

A

Inside cells, around nucleus = nuclear lamina => cell mechanical strength => surface tension

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5
Q

Microtubules?

A

Made of tubulin, more rigid than actin/intermediate filaments

One end is collectively attached to a microtubule organizing center like a centrosome

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6
Q

Actin filaments?

A

Beneath cell membranes, polymers of actin, flexible

Linear
Two dimensional networks
Three dimensional gels

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7
Q

Function of a muscle?

A

Transforms chemical energy into mechanical work

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8
Q

What are T-tubules aka transverse tubules?

A

Ridges/cuts sorta of SR, help with Ca delivery

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9
Q

Thin filaments are composed of?

A

F-actin,
Tropomyosin
Troponin

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10
Q

Thick filaments consists of?

A

Myosin heavy chain

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11
Q

Which bands of a sacromere shrink/stay constant during contraction?

A

I band shrinks (actin only)
A band stays constant (actin/myosin)

=> sacromere changes length overall

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12
Q

Forms of actin?

A

Globular
Single polypeptide monomer = G-actin
Thin filament F-actin

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13
Q

3 major classes of actin?

A

Alpha-actin (skeletal/cardiac/smooth muscle)

Beta- and gamma-actins (non-muscle cells)

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14
Q

Function of tropomyosin/troponins/Ca?

A

Tropomyosin = regulatory protein binds to F actin => reversibly blocks myosin head binding sites

Troponin T and troponin I hold tropomyosin over myosin binding site

Ca from SR => troponin C + troponin I + Troponin T (troponin complex) => confirmational change => exposing attachment site

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15
Q

Major functional/pathway difference between all other cells and smooth muscle/non-muscle cells?

A

Smooth muscle+ non-muscle cells (?) dont contain troponin

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16
Q

Major important thing to know about troponin C structure?

A

AA 12 = glutamate or asparate => provides 1 of 2 negatively charged oxygen molecules for binding positively charged Ca

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17
Q

Function of actin binding proteins?

A

ABPs = group of proteins that regulate actin filament formation/length and actin/myosin interactions

Incl. tropomyosin/troponins, more common in non-muscle/sm

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18
Q

Function of ABP alpha-actinin?

A

Binds actin thin filaments to skeletal muscle Z lines and smooth muscle dense bodies

Spaces thin filaments

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19
Q

3 domains of myosin?

A

Head
Neck
Tail AA sequence

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20
Q

Function of myosin head?

A

Binds actin thin filaments and uses hydrolysis of ATP to ADP to generate force

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21
Q

Function of myosin tail domain?

A

= varies depending on type of myosin

Bind to transport vesicles/combine with other myosins/regulate folding

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22
Q

Function of myosin neck?

A

Serves as lever arm for force transfer between head and tail

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23
Q

General steps of muscle contraction?

A

Excitation

Excitation-Contraction Coupling (transmit signal to myofibrils)

Contraction (myofibrils contract)

Relaxation

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24
Q

Main NT in skeletal muscle? Enzyme breaking it down after?

A

ACh

AChE catalyses hydrolysis of ACh => signal turns off

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25
Q

How do chemical warfare nerve agents work?

A

Bind to AChEsterase in adrenergic/cholinergic synaptic clefts => ACh can’t be degraded => continuous contraction

Agents: Sarin, VX, Soman

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26
Q

Difference between skeletal and cardiac/sm muscle excitation-contraction coupling?

A

Skeletal muscle:
Occurs via mechanical coupling between T tubules/SR to release Ca

Cardiac/sm muscle:
Occurs when signal from nerve/pacemaker cells causes initial increase in Ca => increase in Ca from SR (calcium induced calcium release CICR)

So the difference is CICR

27
Q

Calcium interacts with what molecules in skeletal/cardiac muscle vs smooth muscle?

A

Skeletal/cardiac: troponin/tropomyosin (ABP)

Smooth: caldesmon

28
Q

Which molecule is responsible for the Ca storage in SR?

A

Calsequestin

29
Q

What’s the point of sarco/endoplasmic reticulum Ca-ATPase pump?

A

Pump produces 10k-fold higher Ca inside SR verses sarcoplasm

30
Q

Centronuclear Myopathies (myotubular) characteristics?

A

X linked/autosomal recessive => skeletal muscle nuclei are centered in cells instead of peripheral edges

31
Q

ACh&Myasthenia Gravis (MG) characteristics and most obvious sign?

A

ACh disruption => MG due to antibodies (autoimmune) against ACh receptor @ post-synaptic junction = nicotinic-ACh receptor

Cholinesterase degrades ACh before it’s action

=> eyes/eye lids are affected

32
Q

Two skeletal muscle types?

A

Type I slow twitch

Type IIa/b fast twitch

33
Q

Difference between slow/fast twitch?

A

Slow: less powerful contractions, endurance

Fast: more powerful contractions, susceptible to fatigue

34
Q

Which muscle type stores O2 in myoglobin?

A

Skeletal muscle, Cardiac muscle

35
Q

What causes the endurance in slow twitch fibers?

A

They are able to do aerobic metabolism for more effective oxidative phosphorylation to produce E from TGs/FAs

36
Q

Type IIa fast twitch fibers/intermediate use which form of energy?Mgb content? E source?

A

Intermediate amounts of Mgb

Use aerobic/anaerobic metabolism using creatine phosphate/glycogen

37
Q

E mechanism/source/Mgb of type IIb fast twitch fibers?

A

Do not contain myoglobin/fewer capillaries

Anaerobic metabolism using creatine phosphate/glycogen

White

38
Q

Characteristics of Rhabdomyolysis?

A

Abnormal breakdown of skeletal muscle caused by trauma, disease, medication side effects

=> high levels of Mgb in blood/kidney failure/neuro problems/compartment syndrome => supportive care

39
Q

Predominate mechanism in cardiac muscle is? Type of E metabolism?

A

CICR

Oxidative phosphorylation

40
Q

Mechanism of CICR?

A

1) voltage triggering of L-type calcium channels/dihydropyridine receptor induces Ca inflow (cell)
2) Ca binds to ryanodine receptor on SR
3) RyR releases larger stores of Ca - like IP3
4) Ca activates contraction

41
Q

L-type calcium channels, L stands for? Characteristic?

A

L= long

Stay open for a long time to sustain Ca influx

42
Q

Pacemakers and intercalates disks cause?

A

Synchronized/sequential contractions of heart

From temporal/spatial Ca waves

43
Q

Memorize diagram on slide 40, 44

A

CICR

44
Q

What does smooth muscle lack (chemical)?

A

Troponins

45
Q

Smooth muscle contraction is regulated via CICR using?

A

Calmodulin
Caldesmon
Calponin

46
Q

Two types of contraction in smooth muscle?

A

Tonic contraction: long/slow/little energy use like in vessels

Phasic contraction: rapid like in peristalsis

47
Q

Smooth muscle CICR mechanism?

A

Stimulus => Ca from SR via ryanodine receptor
Or
Influx of external Ca through L-type channels

=> increased Ca initiates actin/myosin interactions via calmodulin and MLCK => contraction

48
Q

Function of calmodulin?

A

Ca activates calmodulin => turns off inhibitory effect of caldesmon/calponin via phosphorylation

Calmodulin activates MLCK (myosin light chain kinase) => activates force generating capabilitites

49
Q

Function of MLCK vs MLCP?

A

MLCK: phosphorylates myosin = contraction

MLCP: dephosphorylates myosin = relaxation:
Myosin light chain phosphatase removes Pi when Ca is low => inactivates myosin => stop contraction = relaxation

50
Q

Creatine phosphate reaction to produce ATP?

A

ATP ===creatine kinase/creatine ==> creatine phosphate (E storage form)

Creatine phosphate —ADP –> ATP

51
Q

Creatine vs creatinine?

A

Creatinine (waste product) = tautomer of creatine phosphate (E storage)

Creatine –creatine kinase–>creatine phosphate

52
Q

McArdle’s disease?

A

Glycogen storage disease type V (GSD-V)

=> absence of myophosphorylase => alternative E source like FA/protein/gluc

53
Q

Which structural element forms the cytoskeleton?

A

Microtubules

=> organelle movement/cilia/flagella/centriole

54
Q

5 basic forms of tubulin and function?

A

Alpha/beta form cytoplasmic microtubules

Gamma form centrosomes

Delta/epsilon are involved in centrioles/mitotic spindle

55
Q

De/Polymerization of microtubule polymers plays a role in?

A

Mitosis

56
Q

Use of microtubule polymerization in cancer therapy?

A

No polymerization = mitotic inhibition = cell death

Inhibit metaphase = no cell proliferation

57
Q

What is dynein?

A

Functions very similar than myosin = large ATPase

58
Q

Which dynein functions in cilia/flagella motility?

A

Axonemal dynein

59
Q

Kinesins play a role in?

A

Intracellular transport (inside cell) towards positive end of microtubule network/ toward plasma membrane

60
Q

How are intermediate filaments build?

A

Alpha helical region of monomer

=> x2 = coiled-coil dimer
=> x4 = staggered tetramer of two coiled-coil dimers
=> x8 = two tetramers packed together
=> x64 = eight tetramers twisted into a rope

61
Q

Function of intermediate filaments?

A

Transmit force/absorb mechanical stress

62
Q

What happens during the power stroke?

A

ADP release

63
Q

What causes actin release?

A

Binding of ATP

64
Q

How is the contraction cycle reset?

A

Hydrolysis of ATP

BioChem Exam 3 (5 decks)

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