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10 Cards in this Set
- Front
- Back
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Name 3 types of muscle and tell which are striated. Which are voluntary and which are involuntary?
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- Skeletal (striated), cardiac (striated) and smooth
- Voluntary: skeletal - Involuntary: smooth and cardiac |
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What does striated mean
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Muscles enclosed by a membrane known as the sarcolema that can be excited by electrical impulses from nerves
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What is the composition of the thick filaments in the sarcomeres?
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Composed of the protein myosin and found in A-bands
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What is the composition of the thin filamets in sarcomeres?
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Composed of the proteins actin, tropomyosin, and troponin. Lie in the I-bands and extend into A-bands (not H zone)
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What kinds of filaments lie in which bands of the sarcomeres?
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Thick - A-bands
Thin - I-bands and extend into A-bands; but not into H zone |
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Describe the structure of myosin. Does it have any enzymatic activity, what kind?
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Is a fibrous protein consisting of 2 intertwined helices w/ a globular head region attached at one end on each
Skeletal mm myosin has ATP-ase activity and binds to insoluble F-actin protein |
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Briefly describe the mechanism of muscle contractions.
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1. Myosin head hydrolyzes ATP, but doesn't release ADP and Pi
2. Myosin head group with ADP and Pi attached rotates through large angle to locate and bind F-actin at ~90 degree angle 3. Binding promotes release of ADP and Pi. Myosin changes head from 90->45 deg angle (lowest energy state of actomyosin bond) by pulling actin toward middle of sarcomere 4. New ATP binds to myosin-F-actin 5. Since myosin-ATP has poor affinity for actin, head is released from F-actin. ATP powers mm contraction. |
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Describe the 3 peptides of troponin and what function they perform.
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Troponin (TpT) - binds to propomyosin and other Tp units
Troponin I (TpI) - inhibits F-actin-myosin interaction and binds other Tp units Troponin C (TpC) - calcium binding polypeptide which is very analogous to calmodium - binds 4 calciums |
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Where are troponin and tropomyosin in muscle?
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In the thin filaments
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What divalent ion plays a crucial regulatory role in mm contraction, and what does it bind to in striated muscle?
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Ca++
Binds to TpC |
