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BioChem Exam 3 > Muscles & Motility > Flashcards

Muscles & Motility Flashcards

(64 cards)

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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
How do chemical warfare nerve agents work?
Bind to AChEsterase in adrenergic/cholinergic synaptic clefts => ACh can't be degraded => continuous contraction Agents: Sarin, VX, Soman
26
Difference between skeletal and cardiac/sm muscle excitation-contraction coupling?
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
Calcium interacts with what molecules in skeletal/cardiac muscle vs smooth muscle?
Skeletal/cardiac: troponin/tropomyosin (ABP) Smooth: caldesmon
28
Which molecule is responsible for the Ca storage in SR?
Calsequestin
29
What's the point of sarco/endoplasmic reticulum Ca-ATPase pump?
Pump produces 10k-fold higher Ca inside SR verses sarcoplasm
30
Centronuclear Myopathies (myotubular) characteristics?
X linked/autosomal recessive => skeletal muscle nuclei are centered in cells instead of peripheral edges
31
ACh&Myasthenia Gravis (MG) characteristics and most obvious sign?
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
Two skeletal muscle types?
Type I slow twitch | Type IIa/b fast twitch
33
Difference between slow/fast twitch?
Slow: less powerful contractions, endurance Fast: more powerful contractions, susceptible to fatigue
34
Which muscle type stores O2 in myoglobin?
Skeletal muscle, Cardiac muscle
35
What causes the endurance in slow twitch fibers?
They are able to do aerobic metabolism for more effective oxidative phosphorylation to produce E from TGs/FAs
36
Type IIa fast twitch fibers/intermediate use which form of energy?Mgb content? E source?
Intermediate amounts of Mgb Use aerobic/anaerobic metabolism using creatine phosphate/glycogen
37
E mechanism/source/Mgb of type IIb fast twitch fibers?
Do not contain myoglobin/fewer capillaries Anaerobic metabolism using creatine phosphate/glycogen White
38
Characteristics of Rhabdomyolysis?
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
Predominate mechanism in cardiac muscle is? Type of E metabolism?
CICR Oxidative phosphorylation
40
Mechanism of CICR?
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
L-type calcium channels, L stands for? Characteristic?
L= long Stay open for a long time to sustain Ca influx
42
Pacemakers and intercalates disks cause?
Synchronized/sequential contractions of heart | From temporal/spatial Ca waves
43
Memorize diagram on slide 40, 44
CICR
44
What does smooth muscle lack (chemical)?
Troponins
45
Smooth muscle contraction is regulated via CICR using?
Calmodulin Caldesmon Calponin
46
Two types of contraction in smooth muscle?
Tonic contraction: long/slow/little energy use like in vessels Phasic contraction: rapid like in peristalsis
47
Smooth muscle CICR mechanism?
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
Function of calmodulin?
Ca activates calmodulin => turns off inhibitory effect of caldesmon/calponin via phosphorylation Calmodulin activates MLCK (myosin light chain kinase) => activates force generating capabilitites
49
Function of MLCK vs MLCP?
MLCK: phosphorylates myosin = contraction MLCP: dephosphorylates myosin = relaxation: Myosin light chain phosphatase removes Pi when Ca is low => inactivates myosin => stop contraction = relaxation
50
Creatine phosphate reaction to produce ATP?
ATP ===creatine kinase/creatine ==> creatine phosphate (E storage form) Creatine phosphate ---ADP --> ATP
51
Creatine vs creatinine?
Creatinine (waste product) = tautomer of creatine phosphate (E storage) Creatine --creatine kinase-->creatine phosphate
52
McArdle's disease?
Glycogen storage disease type V (GSD-V) | => absence of myophosphorylase => alternative E source like FA/protein/gluc
53
Which structural element forms the cytoskeleton?
Microtubules => organelle movement/cilia/flagella/centriole
54
5 basic forms of tubulin and function?
Alpha/beta form cytoplasmic microtubules Gamma form centrosomes Delta/epsilon are involved in centrioles/mitotic spindle
55
De/Polymerization of microtubule polymers plays a role in?
Mitosis
56
Use of microtubule polymerization in cancer therapy?
No polymerization = mitotic inhibition = cell death | Inhibit metaphase = no cell proliferation
57
What is dynein?
Functions very similar than myosin = large ATPase
58
Which dynein functions in cilia/flagella motility?
Axonemal dynein
59
Kinesins play a role in?
Intracellular transport (inside cell) towards positive end of microtubule network/ toward plasma membrane
60
How are intermediate filaments build?
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
Function of intermediate filaments?
Transmit force/absorb mechanical stress
62
What happens during the power stroke?
ADP release
63
What causes actin release?
Binding of ATP
64
How is the contraction cycle reset?
Hydrolysis of ATP

BioChem Exam 3 (5 decks)

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