Muscle Cell Structure Quiz
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Questions and Answers

What happens when Ca$^{2+}$ binds to troponin C (TnC) in the presence of tropomyosin?

  • Ca$^{2+}$ binding to TnC shifts the tropomyosin-troponin complex, relieving inhibition and allowing muscle contraction to proceed. (correct)
  • Ca$^{2+}$ binding to TnC strengthens the inhibition of muscle contraction by the tropomyosin-troponin complex.
  • Ca$^{2+}$ binding to TnC causes dissociation of tropomyosin from actin filaments, preventing muscle contraction.
  • Ca$^{2+}$ binding to TnC has no effect on the tropomyosin-troponin complex or muscle contraction.

    • What is the role of tropomyosin in muscle contraction?

  • Tropomyosin binds lengthwise along actin filaments and, in striated muscle, is associated with a complex of three troponins, regulating the binding of myosin to actin. (correct)
  • Tropomyosin blocks the binding of troponins to actin filaments, preventing muscle contraction.
  • Tropomyosin directly binds to myosin to initiate muscle contraction.
  • Tropomyosin is not involved in regulating muscle contraction.

    • What is the result of the actin filaments sliding past the myosin filaments in muscle contraction?

  • Shortening of both actin and myosin filaments
  • Shortening of the sarcomere without any change in filament length (correct)
  • Lengthening of the sarcomere without any change in filament length
  • Lengthening of both actin and myosin filaments

    • What happens in the absence of Ca$^{2+}$ in relation to the tropomyosin-troponin complex?

    <p>The tropomyosintroponin complex blocks the binding of myosin to actin. (D)</p> Signup and view all the answers

    What is the role of tropomyosin in muscle contraction?

    <p>Tropomyosin binds lengthwise along actin filaments and, in striated muscle, is associated with a complex of three troponins: troponin I (TnI), troponin C (TnC), and troponin T (TnT). (A)</p> Signup and view all the answers

    What happens in the absence of Ca$^{2+}$ in relation to the tropomyosin-troponin complex?

    <p>The tropomyosintroponin complex blocks the binding of myosin to actin. (A)</p> Signup and view all the answers

    What is the result of the actin filaments sliding past the myosin filaments in muscle contraction?

    <p>Shortening of the sarcomere without any change in filament length. (C)</p> Signup and view all the answers

    What happens when Ca$^{2+}$ binds to troponin C (TnC) in the presence of tropomyosin?

    <p>The tropomyosintroponin complex shifts, relieving inhibition and allowing contraction to proceed. (B)</p> Signup and view all the answers

    Which component works in conjunction with troponin to regulate association of tropomyosin and troponins with actin filaments?

    <p>Ca$^{2+}$ (B)</p> Signup and view all the answers

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