Vincent Conquer
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The Anatomy and Function of a Myofibril

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Vincent Conquer
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The Anatomy and Function of a Myofibril, Myofilaments, Actin, Myosin other proteins

Question 1 of 12

1

What is a myofibril?

Select one of the following:

  • the muscle fiber

  • the actin filament

  • the myosin filament

  • columnar protein columns alongside the muscle fiber

Explanation

Question 2 of 12

1

Bodily movements or motion occur when muscles contract or shorten. Which of the following best describes how this occurs?

Select one of the following:

  • kk

  • Actin, when polymerized into filaments, forms the "ladder" along which the myosin filaments "climb" to generate motion.

Explanation

Question 3 of 12

1

Six different proteins and molecules participate in the contraction of a sarcomere, namely:
myosin
actin
tropomyosin
troponin
ATP
Ca2+ ions
 
Some of these combine together to form thick and thin filaments.

Read more: http://slidingfilament.webnode.com/sliding-filament-theory/

Select one of the following:

  • kk

  • jj

Explanation

Question 4 of 12

1

a) Thick filaments - The thick filament is composed of myosin. The projections from the myosin filament are called crossbridges. The crossbridge is believed to be a molecular motor that converts chemical energy into mechanical work.

b) Thin filaments - The thin filament is composed of actin, troponin, and tropomyosin.

Select one of the following:

  • k

  • o

Explanation

Question 5 of 12

1

Regulatory proteins are :

Select one of the following:

  • myosin is a contractile filament

    titin and nebulin are structural proteins

    contractile protein , Actin
    -consists of 2 alpha helical strands of g-actin molecules bonded in series
    -each g-actin has a binding site where the s1 fragment of the myosin cross-bridge complex binds during muscle contraction

    -contractile protein, myosin
    -consists of two heavy (form tail region and two cross-bridges that bind with actin to produce force) and four light chains (that influence cross-bridge cycling kinetics and therefore sarcomere contraction velocity

    -contractile protein
    -consists of two heavy (form tail region and two cross-bridges that bind with actin to produce force) and four light chains (that influence cross-bridge cycling kinetics and therefore sarcomere contraction velocity

    Muscle contractile protein
    Heart and muscle contractile fibres consist of bundles of actin polymers that slide alongside each other by the activity of the motor protein myosin and associated contractile proteins such as troponin and titin

    Muscle contractile protein
    Heart and muscle contractile fibres consist of bundles of actin polymers that slide alongside each other by the activity of the motor protein myosin and associated contractile proteins such as troponin and titin

    regulatory proteins
    proteins that help turn the muscle contraction process on and off

    contractile proteins
    proteins that produce force during muscle contraction

    structural proteins
    proteins that connect the outer layer of myofibrils to the sarcolemma, keep the actin and myosin filaments in proper alignment, and give the myofibrils their elasticity and extensibility

    tropomyosin
    -two per actin filament
    -when muscle is relaxed, covers the myosin-head binding sites on the actin filament

    troponin
    -binds to both actin and tropomyosin
    -has binding site for Ca+2 needed for muscle contraction
    -located at the junction of each successive pair of tropomyosin molecules

    titin
    -stabilizes the alignment of the thick filaments by connecting each myosin filament to both the z line and the m line
    -the titin that extends from the z line to the beginning of the myosin filament is believed to help keep the myosin filaments centered between the z lines
    -helps the sarcomere return to its resting length after the muscle has contracted or been stretched, contributing to the myofibril's elasticity and extensibility

    nebulin
    -extends the length of each actin filament
    -believed to anchor the actin filament to the z-line and help regulate the length of the actin filament

    actin
    -contractile protein
    -consists of 2 alpha helical strands of g-actin molecules bonded in series
    -each g-actin has a binding site where the s1 fragment of the myosin cross-bridge complex binds during muscle contraction

    myosin
    -contractile protein
    -consists of two heavy (form tail region and two cross-bridges that bind with actin to produce force) and four light chains (that influence cross-bridge cycling kinetics and therefore sarcomere contraction velocity

  • proteins that help turn the muscle contraction process on and off

  • proteins that regulate bodily systems and are used in homeostasis

Explanation

Question 6 of 12

1

Titin and nebulin are structural proteins

Select one of the following:

  • True
  • False

Explanation

Question 7 of 12

1

actin
- is a contractile protein
-consists of 2 alpha helical strands of g-actin molecules bonded in series
-each g-actin has a binding site where the s1 fragment of the myosin cross-bridge complex binds during muscle contraction

Select one of the following:

  • True
  • False

Explanation

Question 8 of 12

1

myosin

Select one of the following:

  • -is a contractile protein

  • -consists of two heavy (form tail region and two cross-bridges that bind with actin to produce force) and four light chains (that influence cross-bridge cycling kinetics and therefore sarcomere contraction velocity

  • is a myofilament , a filament of a myofibril

  • All of these are true

Explanation

Question 9 of 12

1

contractile proteins

Select one of the following:

  • proteins that produce force during muscle contraction

  • proteins that bind with troponin

  • are centered with the M-line

  • proteins that build muscle

Explanation

Question 10 of 12

1

structural proteins:
proteins that connect the outer layer of myofibrils to the sarcolemma, keep the actin and myosin filaments in proper alignment, and give the myofibrils their elasticity and extensibility

Select one of the following:

  • True
  • False

Explanation

Question 11 of 12

1

tropomyosin:

Select one of the following:

  • There are two per actin filament.
    Tropomyosin, when muscle is relaxed, covers the myosin-head binding sites on the actin filament.

  • is a myofilament

  • has a calcium ion attached to it

  • is located in the neuromuscular junction

Explanation

Question 12 of 12

1

Fill the blank spaces to complete the text.

Titin
-stabilizes the alignment of the thick filaments by connecting each myosin filament to both the
-the titin that extends from the z line to the beginning of the myosin filament is believed to
-helps the after the muscle has contracted or been stretched, contributing to the

nebulin
-extends the length of each actin filament
-believed to anchor the actin filament to the z-line and help regulate the length of the actin filament

actin
-contractile protein
-consists of 2 alpha helical strands of g-actin molecules bonded in series
-each g-actin has a binding site where the s1 fragment of the myosin cross-bridge complex binds during muscle contraction

myosin
-contractile protein
-consists of two heavy (form tail region and two cross-bridges that bind with actin to produce force) and four light chains (that influence cross-bridge cycling kinetics and therefore sarcomere contraction velocity

Explanation

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