Biochemistry: Concepts and Connections (2nd Edition)
2nd Edition
ISBN: 9780134641621
Author: Dean R. Appling, Spencer J. Anthony-Cahill, Christopher K. Mathews
Publisher: PEARSON
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Chapter 7, Problem 17P
A typical relaxed sarcomere is about 2.3 μm in length and contracts to about 2 μm length. Within the sarcomere, the thin filaments are about 1 μm long and thick filaments are about 1.5 μm long.
a. Describe the overlap of thick and thin filaments in the relaxed and contracted sarcomere.
b. An Individual "step" by a myosin head in one cycle pulls the thin filament about 15 nm. How many steps must each actin fiber make in one contraction?
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A typical relaxed sarcomere is about 2.3 µm in length and contracts
to about 2 µm in length. Within the sarcomere, the thin filaments
are about 1 um long and the thick filaments are about 1.5 um long.
(a) Describe the overlap of thick and thin filaments in the relaxed
and contracted sarcomere.
(b) An individual "step" by a myosin head in one cycle pulls the thin
filament about 15 nm. How many steps must each actin fiber make
in one contraction?
A typical relaxed sarcomere is about 2.3 um in length and contracts to about
2 um in length. Within the sarcomere, the thin filaments are about 1 um
long and the thick filaments are about 1.5 um long.
(a) Describe the overlap of thick and thin filaments in the relaxed and con-
tracted sarcomere.
(b) An individual "step" by a myosin head in one cycle pulls the thin fila-
ment about 15 nm. How many steps must each actin fiber make in one
contraction?
The ability of myosin to walk along an actin filament may be observed with the aid of an appropriately equipped microscope. Describe how such assays are typically performed. Why is ATP required in these assays? How can such assays be used to determine the direction of myosin movement or the force produced by myosin?
Chapter 7 Solutions
Biochemistry: Concepts and Connections (2nd Edition)
Ch. 7 - Prob. 1PCh. 7 - Certain antibodies have been shown to bind only to...Ch. 7 - Antibodies raised against a macromolecular antigen...Ch. 7 - Prob. 4PCh. 7 - Prob. 5PCh. 7 - Prob. 6PCh. 7 - Prob. 7PCh. 7 - Prob. 8PCh. 7 - Prob. 9PCh. 7 - Prob. 10P
Ch. 7 - Prob. 11PCh. 7 - Prob. 12PCh. 7 - Prob. 13PCh. 7 - Suppose your biking partner claims that...Ch. 7 - Prob. 15PCh. 7 - An antibody has been isolated that binds to...Ch. 7 - A typical relaxed sarcomere is about 2.3 m in...Ch. 7 - Each gram of mammalian skeletal muscle consumes...Ch. 7 - A few hours after the death of an animal, the...
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- With regard to muscle contraction, which of the following is an INCORRECT statement with regard to the interactions of filaments that occur in the sarcomere? A. When muscles are relaxed tropomyosin blocks binding sites on actin subunits, which keeps cross-bridges from forming. B. The myosin heads conduct a power stroke motion to slide when bound to actin, to move the "thin" filaments towards the center of the sarcomere. C. During contraction, actin subunits are removed from the ends of the "thin" filaments to shorten actin polymers, thus reducing the length of the sarcomere. D. "Thick" filaments are anchored at the M-line, while "thin" filaments are anchored at the Z-line. E. Numerous myosin heads engage with the actin filaments simultaneously, such that there is no back-slipping during the contraction process.arrow_forwardConsidering the Length-Tension Relationship of skeletal muscle fibers, over stretching a muscle fiber or not stretching a muscle fiber enough, results ina decrease in force developed (during contraction) because: 27. A. An "over-stretched" muscle fiber or an “under-stretched" muscle fiber will not allow Calcium, from the sarcoplasmic reticulum, to adequately diffuse into the cytoplasm. B. An "over-stretched" muscle fiber or an "under-stretched" muscle fiber will not allow an optimum amount of contact and overlap for the contractile proteins. C. An "over-stretched" muscle fiber or an“under-stretched" muscle fiber will not allow the Action Potential to reach the troponin-activation channels. D. An "over-stretched" muscle fiber or an "under-stretched" muscle fiber will not allow the Sodium current to depolarize the membrane. Teurons toarrow_forwardPluripotent stem cells undergo a number of changes as they progress through developmental stages to become the terminally differentiated cell type known as a skeletal muscle myofiber. a) Describe the stages and key anatomic and functional changes that occur during differentiation of myofibers. b) Despite the fact that myofibers are terminally differentiated, muscle can regenerate itself following a trauma or injury. Describe how this can occur.arrow_forward
- As mentioned in class, one additional major use of ATP in skeletal muscle (besides powering the myosin heads) is the recycling of calcium ions back into the sarcoplasmic reticulum after depolarization. The resting concentration of Ca++ in the muscle cell cytoplasm is about 50-100 nM, and the spike concentration after depolarization is about 10-20 μΜ. a) Consider a single sarcomere. What is the number of free calcium ions within the sarcomere at rest? What is the number of free calcium ions after depolarization? b) The major ion pump responsible for calcium ion recycling is SERCA (sarco/endoplasmic reticulum calcium ATPase). SERCA uses one molecule of ATP to pump two calcium ions, and the resting level can be restored in about 10-20 ms. How many molecules of ATP are used in a single sarcomere for pumping calcium in a single "twitch"? c) Assume that a single "twitch" is sufficient to drive one sarcomere from its fully extended length (about 2.5 µm) to its fully contracted length (about 1…arrow_forwardThe 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_forwardThe Sarcomere 2 Thin filaments are often named for which protein? a. actin b. myosin c. troponin d. tropomyosinarrow_forward
- Troponin C has been mutated such that it cannot bind to calcium. Describe the effect of this mutation on sarcomere shortening in skeletal muscle. A complete answer will describe the normal function of troponin C, the normal process of sarcomere shortening, and will describe the overall effect of the mutation on sarcomere shortening based on troponin C's function and its role in the overall process of sarcomere shortening.arrow_forwardDescribe the movement of myosin along an actin filament. Outline the primary molecular steps and explain how this process is used by cells. How many actin monomers within an actin filament would a myosin molecule need to ratchet in order to contract a cell by approximately 1 um? How fast could a non-muscle cell make this contraction compared to a muscle cell if the relative rates of myosin walks on F-actin are 4.5 um/sec and 0.04 um/sec for myosin II and I respectively?arrow_forwardMyosin II has a duty ratio of 10 percent, and its step size is 8 nm. In contrast, myosin V has a much higher duty ratio (about 70 percent) and takes 36-nm steps as it walks down an actin filament. What differences between myosin II and myosin V account for their different properties?arrow_forward
- Certain multi-headed myosins bind cooperatively to actin filaments. The binding interaction is mainly electrostatic in nature, so the presence of additional salt (ions) in solution can interfere with binding; ions will tend to associate with charged residues on the two proteins, blocking electrostatic attractions that would otherwise take place. Briefly describe the expected shape of the binding curve for one of these myosins, and what will happen to the shape when the salt concentration increases.arrow_forwardChoose the best description of how myosin and actin are arranged within the two types of protein filaments in myofibrils. a.) Actin makes up the think filaments, and myosin makes up the thin filaments. b.) Myosin makes up the think filaments, and actin makes up the thin filaments. c.) Myosin and actin are randomly interspersed in the think filaments but are absent from the thin filaments. d.) Myosin and actin overlap with each other to make up both the think and thin filaments.arrow_forwardWhich of the following is true concerning the role of Calcium in the contraction of muscle- cells? 23. A. skeletal muscle cells require an extracellular inward-Calcium-current to stimulate the burst of Calcium from the sarcoplasmic reticulum. B. smooth muscle cells require an extracellular inward-Calcium-current to stimulate the burst of Calcium from the sarcoplasmic reticulum. C. cardiac muscle cells require an extracellular inward-Calcium-current to stimulate the An burst of Calcium from intracellular stored-Calcium-organelles. D. No type of muscle cell requires an extracellular inward-Calcium current for normal contractile-function.arrow_forward
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