Muscle Physiology and Motor Proteins Quiz
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Questions and Answers

What is the primary role of motor proteins in relation to the cytoskeleton?

  • To synthesize proteins
  • To support cell shape
  • To facilitate cellular movement (correct)
  • To generate energy

    • Kinesin and dynein are both types of motor proteins that transport materials along microtubules.

    True

    What are the two main types of protein structures that make up the cytoskeleton?

    Microtubules and microfilaments

    Myosin interacts with ATP and exists mostly as a ______.

    <p>dimer</p> Signup and view all the answers

    Match the types of motor proteins to their primary function:

    <p>Kinesin = Transport cargo towards the positive end of microtubules Dynein = Transport cargo towards the negative end of microtubules Myosin = Facilitates muscle contraction and movement Myofilament = Support and structure in muscle cells</p> Signup and view all the answers

    What is the primary purpose of T-tubules in muscle fibers?

    <p>Conduct action potentials into the muscle fiber</p> Signup and view all the answers

    The sliding filament theory was proposed by Hugh Huxley in 1954.

    <p>True</p> Signup and view all the answers

    What are the three components of the troponin complex?

    <p>TnI, TnC, TnT</p> Signup and view all the answers

    The _______ is the basic functional unit of a muscle fiber.

    <p>sarcomere</p> Signup and view all the answers

    Match the following muscle contraction proteins with their roles:

    <p>Actin = Thin filament Myosin = Thick filament Troponin = Regulatory protein involved in contraction Tropomyosin = Covers actin binding sites</p> Signup and view all the answers

    What type of muscle tissue is under voluntary control?

    <p>Skeletal Muscle Tissue</p> Signup and view all the answers

    Smooth muscle tissue contracts involuntarily.

    <p>True</p> Signup and view all the answers

    What structure attaches muscles to bones?

    <p>Tendon</p> Signup and view all the answers

    Muscle fibers are wrapped in __________.

    <p>perimysium</p> Signup and view all the answers

    Match the muscle types with their characteristics:

    <p>Skeletal Muscle = Voluntary control Smooth Muscle = Involuntary control Cardiac Muscle = Heart contractions Striated Muscle = Striped appearance</p> Signup and view all the answers

    What muscle type is responsible for the contractions of the heart?

    <p>Cardiac Muscle</p> Signup and view all the answers

    All muscle tissues contain a single nucleus.

    <p>False</p> Signup and view all the answers

    What is the role of actin and myosin in muscle contraction?

    <p>They interact to cause muscle contraction.</p> Signup and view all the answers

    What is the primary functional unit of muscle contraction?

    <p>Sarcomere</p> Signup and view all the answers

    The I band corresponds with the region where myosin is found.

    <p>False</p> Signup and view all the answers

    Name the protein that stabilizes actin filaments.

    <p>Nebulin</p> Signup and view all the answers

    The thick filament in a sarcomere is primarily made of _____ molecules.

    <p>myosin</p> Signup and view all the answers

    Which protein stops the depolymerization of actin filaments?

    <p>Tropomodulin</p> Signup and view all the answers

    Match the following components of muscle contraction with their functions:

    <p>Myosin = Main component of thick filaments Actin = Main component of thin filaments Nebulin = Stabilizes actin filaments Tropomodulin = Prevents actin depolymerization</p> Signup and view all the answers

    Describe how the sarcomere is shortened during contraction.

    <p>The myosin heads pull actin filaments toward the center, decreasing the distance between Z lines.</p> Signup and view all the answers

    In a sarcomere, each thick filament is surrounded by six thin filaments.

    <p>True</p> Signup and view all the answers

    What is the role of tropomyosin in muscle contraction?

    <p>It blocks binding sites on actin</p> Signup and view all the answers

    Troponin and tropomyosin are involved in exposing the active sites on actin during muscle contraction.

    <p>True</p> Signup and view all the answers

    What is needed for the myosin head group to detach from the actin filament?

    <p>ATP</p> Signup and view all the answers

    The _____ ion binds to troponin to initiate muscle contraction.

    <p>calcium</p> Signup and view all the answers

    Match the following terms with their corresponding roles:

    <p>Tropomyosin = Blocks binding sites on actin Troponin = Regulates tropomyosin movement Myosin = Binds to actin during contraction ATP = Provides energy for muscle relaxation</p> Signup and view all the answers

    What happens to tropomyosin when calcium ions bind to troponin?

    <p>It moves away from the active sites on actin</p> Signup and view all the answers

    Without ATP, myosin heads will detach from the actin filaments.

    <p>False</p> Signup and view all the answers

    What occurs during the cross-bridge attachment phase?

    <p>Myosin binds to exposed active sites on actin.</p> Signup and view all the answers

    What happens during the pivoting step of muscle contraction?

    <p>Myosin head releases ADP and a phosphate group</p> Signup and view all the answers

    Myosin is permanently bound to actin until ATP is released.

    <p>False</p> Signup and view all the answers

    What is released when myosin splits ATP?

    <p>ADP and a phosphate group</p> Signup and view all the answers

    The __________ step involves the myosin head pivoting toward the center of the sarcomere.

    <p>pivoting</p> Signup and view all the answers

    Match the following steps of muscle contraction with their descriptions:

    <p>Pivoting = Myosin head moves toward the center and releases ADP Cross-bridge Detachment = ATP binds to myosin allowing it to detach from actin Myosin Reactivation = Myosin splits ATP to regain energy Calcium Regulation = Controls muscle contraction at the fiber level</p> Signup and view all the answers

    What is required for myosin reactivation?

    <p>ATP</p> Signup and view all the answers

    The force of contraction decreases as calcium concentration increases.

    <p>False</p> Signup and view all the answers

    What role does ATP play in muscle contraction?

    <p>It provides energy for myosin to pivot and detach.</p> Signup and view all the answers

    Study Notes

    Motor Proteins

    • Motor proteins are involved in movement within cells.
    • Microtubules and microfilaments are structures in cells made up of proteins (actin and tubulin).
    • Organisms move in three ways:
      • reorganizing cytoskeleton
      • carrying things around cells along microtubules with motor proteins
      • pulling on elements of cytoskeleton by motor proteins

    Motor Protein Kinesin

    • Kinesin is a motor protein that moves vesicles along microtubules.
    • Kinesin carries cargo to the microtubule-organizing center (MTOC).
    • Kinesin operates along microtubules using ATP (adenosine triphosphate) as fuel.

    Motor Protein Dynein

    • Dynein is another motor protein.
    • Dynein carries cargo back to the microtubule organizing center (MTOC).
    • Dynein operates along microtubules using ATP.

    Structure of Kinesin

    • Kinesin has a head, stalk, and tail.
    • ATP binds to the head and alters the shape to move along microtubules.

    Motor Protein Toolbox

    • There are different types of kinesins and myosins.
    • Myosin and kinesin are involved in cellular transport.

    Myosin Phylogeny

    • Myosin is a protein family, and there is a phylogenetic tree showing the relationships between different types of myosins.

    Muscle Organization

    • Muscles attach to bones by tendons.
    • Tendons attach to bone, and ligaments attach to bone.
    • Muscles are made up of fascicles.
    • Fascicles are a bundle of muscle fibers (cells).
    • Muscle fibers (cells) are surrounded by endomysium.
    • Perimysium surrounds fascicles.
    • Epimysium surrounds all the fascicles.
    • At the cellular level, the individual muscle cells are called muscle fibers or cells.

    Muscle Fibers

    • Muscle fibers (cells) have many nuclei.
    • Muscle fibers contain many myofibrils.

    Types of Muscle Tissue

    • Skeletal muscle: striated, voluntary movement
    • Smooth muscle: not striated, involuntary control
    • Cardiac muscle: striated, involuntary control

    Sarcomere

    • The sarcomere is the functional unit of skeletal muscles.
    • The sarcomere contains thick and thin filaments.
    • The thick filaments are primarily composed of myosin.
    • Thin filaments are primarily composed of actin.
    • The Z line is on the ends of the sarcomere. This stabilizes the filaments.

    Sliding Filament Theory

    • The Sliding Filament Theory describes how muscles contract.
    • Myosin heads bind to actin.
    • Myosin heads pivot and pull thin filaments.
    • Sarcomeres shorten.
    • The theory was proposed by Huxley and Niedergerke in 1954.

    Muscle Contraction

    • The force of muscle contraction is dependent on the interactions between actin and myosin.
    • ATP drives the sliding contraction of filament.
    • Calcium ions (Ca2+) are essential mediators by triggering the interaction between actin and myosin.

    Thick Filament

    • Myosin molecules are arranged hexagonally in thick filaments.
    • There are ~300 myosin molecules in each section of thick filaments.
    • Myosin head groups bind to actin molecules.

    Thin Filaments

    • Actin monomers form thin filaments.
    • These filaments contain tropomyosin and troponin complexes.
    • These proteins control the interaction between actin and myosin.

    Myosin Head

    • Myosin heads have ATP binding sites which also drive the myosin head group movement.

    Cross-Bridge Cycle

    • ATP hydrolysis releases energy which causes myosin head to pivot.
    • ADP and phosphate from ATP bind and are released throughout the cycle.

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    Description

    Test your knowledge on the roles of motor proteins within the cytoskeleton and muscle physiology. This quiz covers the primary functions of various muscle types, structures involved in muscle contraction, and significant theories in muscle function, including the sliding filament theory. Dive into the details of muscle fibers, T-tubules, and the troponin complex!

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