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Physiology > Module 4: Lecture 2 > Flashcards

Module 4: Lecture 2 Flashcards

1
Q

True or False
Titin is the largest protein in the body

A

True

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2
Q

Titin contains how many amino acids?

A

27,000

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3
Q

What is the molecular weight of Titin?

A

3 million daltons

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4
Q

Which description of the sarcomere organization is correct?

a) The A- band contains no thin filaments
b) The H-zone contains no thin filaments
c) The z-discs are contained within the A-band
d) The I-band contains some thick filaments

A

B

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5
Q

How is your A-band defined?

A

based on the length of your thick filaments however there is an overlap of thin filaments as well

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6
Q

The Z-discs are contained in which band A or I?

A

I

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7
Q

What does your I-band contain?

A

it goes from one thick filament of one sarcomere to another thick filament of a second sarcomere

  • z-line is included
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8
Q

What is the H-band

A
  • From M-line to thick filaments where there is no overlap of thin filaments
  • ONLY THICK FILAMENTS
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9
Q

True or False
Muscle contraction does not necessarily cause “shortening” of the muscle

A

True because of isometric contractions

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10
Q

What does the state of contraction refer to?

A

state in which your actin and myosin are forming cross bridges and generating force

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11
Q

What happens after a contraction of a muscle

A

relaxation of a muscle

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12
Q

True or False
The overlap for your thick and thin filaments in necessary for your cross-bridges to actually form

A

True

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13
Q

What is the signal that allows for the process of muscle contraction?

A
  • the action potential from the neuromuscular junction
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14
Q

What molecule is the key that signals your actin and myosin cross-bridges to form?

A

increase in cytosolic calcium

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15
Q

What are your thin filaments made up of?

A
  • quaternary structure (made up of multiple different protein chains)
  • Globular actin
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16
Q

If we polymerize G-actin into a long chain we will form what?

A
  • Filamentous actin
  • aka F-actin
17
Q

If we take 2 F-actin filaments and intertwine them what do we get?

A

Actin helix

18
Q

How do we regulate the binding site on the actin filaments?

A
  • tropomyosin
    (regulatory protein)
  • they are intertwined on that actin helix physically blocking the binding site for myosin
19
Q

What does troponin do?

A

regulates tropomyosin

  • sensor about when the muscles is activated or not
20
Q

What are the 2 key regulatory molecules that will allow muscles to contract or not?

A
  1. Troponin
  2. Tropomyosin
21
Q

A single tropomyosin molecule can block how many actin molecules?

A

about 7 actin molecules

22
Q

How many troponin molecules is needed to regulate a single tropomyosin

A

1

23
Q

Troponin has 3 subunits which are what?

A
  1. T, Tropomyosin
  2. I, Inhibitory
  3. C, Calcium
24
Q

What does the first subunit of troponin (T) do?

A

physically interacting with the tropomyosin molecule itself

  • holding it in close proximity to the actual tropomyosin molecule
25
Q

What does the second subunit of troponin (I) do?

A

keeps it in that inhibitory state and ensures that those binding sites are blocked

26
Q

What does the third subunit of troponin (C) do?

A

responsible for sensing when a muscle contraction should be occurring

  • calcium binds to troponin C and induces the conformational change, which removes inhibition
27
Q

What is the thick filament made up of?

A
  • lots of myosin molecules
28
Q

A single myosin molecule is made up of what?

A
  • 2 heavy chains
  • 4 light chains
29
Q

what does dimer mean?

A

composed of two heavy chains that are intertwined with their tail regions in this helical form

30
Q

Within the head of a myosin molecule what are the 2 binding sites?

A
  1. Actin binding site
    - binds to the thin filament to form the cross-bridge
  2. ATP binding site
    - where we hydrolyze ATP to perform a cross-bridge cycle
31
Q

True or False
The myosin heads are coming out from both directions away from the M-line

A

True

32
Q

One heavy chain contains what?

A
  • 1 tail
  • 1 head
33
Q

What do light chain contain?

A

specialized protein that stabilize the head
(also a site for regulation)

  • essential light chain
  • regulatory light chain
34
Q

One heavy chain has how many accompanying light chains?

A

2

35
Q

What enzyme is also found at the ATP binding site?

A

ATPase

36
Q

What are the 4 steps of the cross-bridge cycle?

A
  1. Binding between the myosin head and the thin filament
  2. Movement of the cross-bridges (Power stroke)
  3. Detachment of the cross-bridges: detach myosin from thin filament
  4. Re-energize the myosin head so it can re-attach to a thin filament repeating the cycle
37
Q

What is a Power Stroke?

A

step in which the myosin head physically pulls the myofilament inwards towards the M-line

38
Q

From rest to contracted sarcomere, what happens to the A-band, I-band, H-zone and overall sarcomere length?

A

A-band: no change
- pull thin filaments towards M-line

I-band: Shorten
- will decrease as the thin filaments are being pulled the thick filaments will get closer to the z-line

H-zone: Shorten
- as thin filaments come closer to M-line the H-zone will decrease as thin filaments overlap thick filaments

Sarcomere: Shorten
- Z-lines are getting closer to eachother

39
Q

True or False
When we are contracting our thin and thick filaments will not actually change in length but their overlapping distances will be affected

A

True

Physiology (27 decks)

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