Contractile Proteins

Question 1

What do muscle fibers form from

Answer 1

a syncytium; single, multinucleated cell, no cell membranes bet cells to interrupt signaling.

Question 2

What does skeletal muscle use for fuel

Answer 2

fatty acids and ketone bodies and glucose (only when it has to)

Question 3

What does it use maximally

Answer 3

muscle glycogen. it can withstand anaerobic conditions better than other types of muscle

Question 4

If cardiac muscle becomes ischemic:

Answer 4

it dies; myocardial infarction. Don’t have glycogen stores. No cori cycle.

Question 5

What does skeletal muscle have as a reserve for ATP

Answer 5

phosphocreatine

Question 6

What are featurs of cardiac muscle

Answer 6

1. totally aerobic metabolism
2. oxidizes glucose, and ketone bodies
3. stores some energy in form of phosphocreatine

Question 7

what are markers for myocardial infarction

Answer 7

1. creatine kinase (CK)
2. Glutomate oxaloacetate transaminase (GOT)
3. Troponin
4. Lactate Dehydrogenase

Question 8

What happens when you have onset of chest pain? which enzymes get released?

Answer 8

Troponin goes up really high at earliest time point, then creatine kinase and then lactate dehydogenase last.

Question 9

whats the LD flip (lactate dehydrogenase)

Answer 9

5 diff isoforms.
Reticulo endothelial form is at highest level typically. If you see cardiac form go above that, its typical of a heart attack.

Question 10

The I band is usually just:

Answer 10

actin (thin filaments only) does not span entire lenth of thin filaments

Question 11

How many polypeptide chains does myosin have

Answer 11

6; 2 heavy chains (fibrous; dont dissolve) that have large globular “head” which is ATPase
4 light chains; complex with heads–>regulatory

Question 12

how is myosin formed

Answer 12

1. two heavy chains coil from carboxy terminus.
2. amino terminus forms globular heads.
3. light chains ass with head region.
4. cleavage with trypsin & and papain results in heavy and light meromyosin.

Question 13

what are the thin filaments composed of

Answer 13

actin, troponin, and tropomyosin.

Question 14

what does tropomyosin do

Answer 14

regulates actin/myosin interaction

Question 15

what does troponin do

Answer 15

binds Ca++

Question 16

what is actin c omposed of

Answer 16

1. G actin: ind globular actin molecules

2. F actin: fibrous complex of G actin molecules

Question 17

what does each ind G actin have bound to it

Answer 17

ADP; however ATP/actin interaction is NOT directly involved in muscle contraction.

Question 18

which troponin binds to caclium

Answer 18

Troponin C

Question 19

Z line

Answer 19

where thin filaments attach

Question 20

M line

Answer 20

where thick filaments attach

Question 21

what is A band composed of

Answer 21

thick filaments; spans entire length inc region of overlap with thin filaments

Question 22

what doesnt change upon contraction

Answer 22

A band

Question 23

what dissapears during contraction

Answer 23

H zone

Question 24

What gets smaller during contraction

Answer 24

I band and H zone

Question 25

the biggset polypeptide identified;

Answer 25

titin; protein that extends from M line to Z line (half the length of sacromere); regulates sarcomere length and prevents over extension

Question 26

When nothing is bound to myosin it has high____for actin. When ATP binds, it releases, it has ____affinity. When ATP is hydrolyzed we start to get some affinity for ____and myosin head gets cocked and changes conformation and starts to bind to actin. _____phosphate falls off and we tighten affinity then ____falls off and we go back to original conformation which forms the powerstroke.

Answer 26

affinity; NO; actin; inorganic; ADP

Question 27

Explani muscle contraction

Answer 27

1. nerve impulse stimulates muscle cell
2. muscle cell releases intracellular Ca++ from SR
3. Ca++ binds to troponin C, changing its conformation
4. change in troponin C results in conformational change in tropomyosin
5. exposes myosin binding sites on actin

Question 28

what is sarcolemma

Answer 28

plasma membrane of muscle cell and has deep invaginations called T-tubules which are in close proximity to SR which releases calcium.

Question 29

Smooth muscle does not contain ____

Answer 29

troponin; tropomyosin is regulated with a calcium/calmodulin (CaCM) regulated protein called caldesmon

Question 30

Smooth muscle has a unique myosin light chain called

Answer 30

myosin p-light chain; CaCM activates a myosin light chain kinase (MLCK) enzyme that phosphorolates myosin p- light chain and activates it.

Question 31

Ca++/calmodulin modulates many proteins including:

Answer 31

cyclic nucleotide phosphoiesterase; lowers level and cAMP and shuts down PKA and activates PKC signaling

Question 32

what are targets of Ca++/calmodulin protein kinsae

Answer 32

1. myosin light chain kinase
2. cAMP specific phosphodiesterase
3. NO synthase
4. PI-3 Kinase

Question 33

How does smooth muscle contraction work

Answer 33

1. activate reg protein
2. binds to caldesmin which moves tropomyosin out of the way so actin and myosin can bind
3. Need to phosphorolate myosin light chain via MLCK which is also act by CaCM.