Human Anatomy (9th Edition)
9th Edition
ISBN: 9780134320762
Author: Frederic H. Martini, Robert B. Tallitsch, Judi L. Nath
Publisher: PEARSON
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Textbook Question
Chapter 9, Problem 1RFT
Active sites on actin become available for binding when
(a) calcium binds to troponin.
(b) troponin binds to tropomyosin.
(c) calcium binds to tropomyosin.
(d) actin binds to troponin.
Expert Solution & Answer
Summary Introduction
Introduction:
Muscles are made up of two main protein filaments namely, a thick filament that is made up of a protein called myosin and a thin filament that is composed of a protein known as actin. When these two filaments crossover one another in a row of repetitive events then muscle contraction takes place.
Answer to Problem 1RFT
Correct answer:
Thin filament consists of regulatory proteins called tropomyosin and troponin and the calcium ions binds with the troponin.
Explanation of Solution
Explanation for the correct answer:
Option (a) is given as calcium binds to troponin. The muscle contraction takes place in a series of steps. The cycle starts with electrical events in the sarcolemma. This accelerates the generation of calcium ions from the cisternae of the sarcoplasmic reticulum. The calcium ions then enter the zone of overlap. The next step involves binding of these calcium ions to troponin in the complex of troponin-tropomyosin. This alters the position and rolls the tropomyosin molecule away from the active sites present on the actin. This makes the active sites exposed for the formation of cross-bridges. Hence option (a) is correct.
Explanation for the incorrect answers:
Option (b) is given as troponin binds to tropomyosin. Troponin binds to the troponin-tropomyosin complex and rolls away from the tropomyosin complex. So, it is a wrong answer.
Option (c) is given as calcium binds to tropomyosin. Calcium binds to the troponin molecule instead of tropomyosin molecule. So, it is a wrong answer.
Option (d) is given as actin binds to troponin. Troponin binds to the calcium and makes actin sites exposed. So, it is a wrong answer.
Hence, option (b), (c) and (d) are incorrect.
Conclusion
Therefore, it can be concluded that calcium ions bind to the troponin and this troponin then binds to the troponin-tropomyosin complex, making active sites exposed during muscle contractions.
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Students have asked these similar questions
In muscle cells, magnesium ions compete with calcium ions for binding sites on troponin molecules. If a person has too high a concentration of magnesium ions in the blood, magnesium ions can prevent calcium ions from binding troponin.
A) What effect would this have on muscle contraction (strengthen, weaken, or no effect)?
B) Use your knowledge of how muscle fibers contract to explain your answer in part A.
During muscular contraction, cross-bridges form between _____ and _____ .
Multiple Choice
a) myosin, tropomyosin
b) myosin, troponin
c) troponin, calmodulin
d) actin, tropomyosin
e) actin, myosin
28) the large protein that attaches to myosin and stabilizes it when the sarcomere shortens is:
a) M line
b) H zone
c) I band
d) A band
Chapter 9 Solutions
Human Anatomy (9th Edition)
Ch. 9 - 1. Active sites on actin become available for...Ch. 9 - Prob. 2RFTCh. 9 - Prob. 3RFTCh. 9 - 4. Another name for a muscle that is a prime mover...Ch. 9 - Prob. 5RFTCh. 9 - Prob. 6RFTCh. 9 - 7. The theory that explains muscle contraction is...Ch. 9 - Prob. 8RFTCh. 9 - Label the illustrations to the right as...Ch. 9 - Prob. 1RC
Ch. 9 - 2. The ability to recover from injuries in older...Ch. 9 - Prob. 3RCCh. 9 - Prob. 4RCCh. 9 - Prob. 5RCCh. 9 - A motor unit from a skeletal muscle contains 1500...Ch. 9 - 7. What is the role of the zone of overlap in...Ch. 9 - Several anatomy students take up weight lifting...Ch. 9 - Prob. 2CT
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- The organization of myosin in smooth and striated muscle: A.) differ because smooth muscle lacks sarcomeres B.) is identical but the organization of actin is different C.) is identical but the isoforms of myosin differ D.) differ because striated muscle myosin forms filaments but smooth muscle myosin does not ATP is required for: a.) the phosphorylation of the myosin head in smooth muscle b.) the movement of tropomyosin on the actin filament c.) the swing of the myosin lever arm d.) A and B e.) tethering troponin I to troponin Carrow_forward1) Paula is a scientist who is developing a drug called Fremtol that will be used to treat muscle spasms. This drug acts on specific skeletal muscles to (1) block the release of Ca2+ ions from the sarcoplasmic reticulum, (2) inhibit the pivoting ability of the myosin heads of the thick filaments, and (3) block the production of ATP by the mitochondria in skeletal muscles. By using this drug, contraction of certain skeletal muscle fibers is reduced, which keeps those muscles from producing spasms. In the above scenario, Fremtol’s effect of blocking the pivoting ability of the myosin heads of the thick filaments would have which of the following consequences? a. decreased release of acetylcholine at the neuromuscular junction b. inhibition of the power stroke c. reduced production of myoglobin d. All of the above e. None of the above 2) Paula is a scientist who is developing a drug called Fremtol that will be used to treat muscle spasms. This drug acts on specific skeletal muscles to…arrow_forward2) Paula is a scientist who is developing a drug called Fremtol that will be used to treat muscle spasms. This drug acts on specific skeletal muscles to (1) block the release of Ca2+ ions from the sarcoplasmic reticulum, (2) inhibit the pivoting ability of the myosin heads of the thick filaments, and (3) block the production of ATP by the mitochondria in skeletal muscles. By using this drug, contraction of certain skeletal muscle fibers is reduced, which keeps those muscles from producing spasms. In the above scenario, Fremtol’s effect of blocking the release of Ca2+ ions from the sarcoplasmic reticulum would most directly prevent which the following? a. activation of tropomyosin b. activation of troponin c. activation of actin d. All of the above e. None of the abovearrow_forward
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