Study Guide for Campbell Biology
11th Edition
ISBN: 9780134443775
Author: Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Jane B. Reece, Martha R. Taylor, Michael A. Pollock
Publisher: PEARSON
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Textbook Question
Chapter 50, Problem 18TYK
How does calcium affect muscle contraction?
- a. It is released from the T tubules in response to an action potential and initiates contraction.
- b. The binding of acetylcholine opens calcium channels in the plasma membrane, creating an action potential that travels down the T tubules.
- c. It binds to tropomyosin and helps to stabilize cross-bridge formation.
- d. Its binding to troponin causes tropomyosin to move away from the myosin-binding sites on the actin filament.
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What event causes a troponin-tropomyosin complex to regain its original shape in muscle relaxation? a. stimulation of ACh receptors b. diffusion of Na+ back into transverse tubules c. return of Ca2+ into the sarcoplasmic reticulum d. breaking of the bond with tropomyosin
What do skeletal muscle contractions share in common with smooth muscle contractions?a. Both types of contractions do not require calcium ions for a contraction to occur.b. Both types of contractions generate little force or a weak force.c. Both types of contractions consume very little ATP.d. Both types of contractions result from thick and thin filaments sliding past one another.
What might happen if skeletal muscle lacked tropomyosin?
A.
The striation pattern would disappear.
B.
Ca2+ levels in the muscle would decrease.
C.
Actin and myosin would not be able to form cross-bridges.
D.
Acetylcholine would not be released into the synaptic cleft.
E.
Myosin and actin would form cross-bridges whenever ATP is available.
Chapter 50 Solutions
Study Guide for Campbell Biology
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- Which is a false statement about skeletal muscle structure?a. A myofibril is composed of multiple muscle fibers.b. Most skeletal muscles attach to bones by connective-tissue tendons.c. Each end of a thick filament is surrounded by six thin filaments.d. A cross-bridge is a portion of the myosin molecule.e. Thin filaments contain actin, tropomyosin, and troponin.arrow_forwardWhat happens in a muscle twitch?a. Myosin grabs a thick myofilament.b. Sarcomeres shorten during the contraction phase.c. ATP is put back in the sarcoplasmic reticulum during the refractory phase.d. A threshold stimulus must be reached before anything will happen.e. Thin myofilaments are pulled toward the center of a sarcomere.arrow_forwardWhat structure on a muscle fiber is composed of largely two varieties of contractile proteins--actin and myosin--which slide past each other during muscle activity to bring about shortening or contraction of muscle cells? A. myofilament B. sarcoplasmic reticulum C. transverse tububle D. sarcomeresarrow_forward
- What structure in skeletal muscle cells functions in calcium storage? a.myofibrillar network b.sarcoplasmic reticulum c.intermediate filament network d.mitochondriaarrow_forwardWhich statement about striated skeletal muscle is true? A. The tension generated by a muscle is invariable. B. Mechanical summation of twitches in a muscle fiber leads to a graded increase in the tension that is above that generated by a single twitch. C. A single action potential arriving at the neuromuscular junction is not sufficient to cause a muscle fiber to twitch. D. Muscle twitches are able to mechanically sum when Ca2+ is quickly and completely removed from the sarcoplasm between action potentials. E. An action potential in the muscle cell activates contraction by releasing Na+ into the sarcoplasm.arrow_forwardThe primary role of calcium in skeletal muscle contraction? Select one: a. Cause depolarization of the sarcolemma b. Cross-bridge cycle between actin and myosin C. Provides energy necessary for contraction d. Causes muscle relaxation e. Regulate ionic composition of the cellarrow_forward
- What happens when myosin filaments hydrolyze ATP molecules in muscles? a. Actin–myosin complexes dissociate, leading to muscle contraction. b. Actin–myosin complexes dissociate, leading to muscle relaxation. c. Actin–myosin complexes are formed, leading to muscle contraction. d. Actin–myosin complexes are formed, leading to muscle relaxation.arrow_forwardMyosin binds to actin, then bends. What is ATP needed for next? A. to pump the Ca++ “keys” back into the sarcoplasmic reticulum B. to replace the strap and cover the binding sites C. to give feedback to the neuron that contraction occurred D. to un-bind myosin from actin and re-set for another powerstroke.arrow_forwardWhen a muscle fiber is stretched from 60% of its optimal length to Lo, what change or changes are happening on the cellular level (MULTIPLE SELECT)? A. Increased calcium release from the SR B. Increased firing of action potentials from the alpha motor neuron C. Increased rate of myosin ATPase activity D. Increased number of actin-myosin bridges E. Increased stretch on titin, producing more passive forcearrow_forward
- What does ATP binding to myosin head triggers? a. Its association with microtubules b. Its dissociation from actin microfilament c. Conformational change and rotation of myosin head d. Its association with actin microfilamentarrow_forwardWhich protein is not part of the thin filament in a muscle fiber? A. Actin B. Myosin C. Tropomyosin D. Troponinarrow_forwardWhat role (function) does calcium have within a muscle fiber? a. trigger muscle potentials along t-tubules b. trigger contraction by causing the formation of cross bridges c. trigger exocytosis of ACh across the synaptic space d. trigger action potentials along axons e. open voltage gates within the sarcoplasmic reticulum 2. Which of the following are regulatory proteins that allow a muscle fiber to contract when calcium is present? (select all that apply) dystrophin troponin myosin tropomyosin actin 3. During this phase of an action potential, potassium ions exit the cell through voltage gated potassium channels. a. depolarization b. repolarization c. glycolysis d. cross bridge formationarrow_forward
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