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    what is the role of tropomyosin in skeletal muscles

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    The functions of tropomyosin in skeletal muscle include: (1) Sliding on actin to produce shortening (2) Release Ca+2 after initiation of contraction (3) Acting as "relaxing protein" at rest by covering up the sites where myosin binds to actin (4) Generates ATP NEET Practice Questions, MCQs, Past Year Questions (PYQs), NCERT Questions, Question Bank, Class 11 and Class 12 Questions, and PDF solved with answers

    The functions of tropomyosin in skeletal muscle include: (1) Sliding on actin to produce shortening (2) Release Ca+2 after initiation of contraction (3) Acting as "relaxing protein" at rest by covering up the sites where myosin binds to actin (4) Generates ATP Practice questions, MCQs, Past Year Questions (PYQs), NCERT Questions, Question Bank, Class 11 and Class 12 Questions, NCERT Exemplar Questions and PDF Questions with answers, solutions, explanations, NCERT reference and difficulty level

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    The functions of tropomyosin in skeletal muscle include:

    (1) Sliding on actin to produce shortening

    (2) Release Ca+2 after initiation of contraction

    (3) Acting as "relaxing protein" at rest by covering up the sites where myosin binds to actin

    (4) Generates ATP Q55: 65% From NCERT

    Subtopic:  Skeletal Muscle: Myofilaments |

    Ca+2 bind ________ in the skeletal muscles and leads to exposure of the binding site for ________ on the filament _______:

    (1) Troponin, myosin, actin

    (2) Troponin, actin, relaxin

    (3) Actin, myosin, troponin

    (4) Tropomysin, myosin, actin

    Q56: 80% From NCERT

    Subtopic:  Excitation Contraction Coupling I |

    Following is the figure of actin (thin) filaments. Identify A, B and C:

    (1) A - Tropomyosin, B - Troponin, C - F-actin

    (2) A - Troponin, B - Myosin, C - Tropomyosin

    (3) A - Troponin, B - Tropomyosin, C - Myosin

    (4) A - Troponin, B - Tropomyosin, C - F-actin

    Q57: 77% From NCERT

    Subtopic:  Skeletal Muscle: Myofilaments |

    The above figure is related with myosin monomer (meromyosin). Identify A to C:

    (1) A - head, B - cross arm, C - GTP binding sites

    (2) A - head, B - cross arm, C - Ca+2 binding sites

    (3) A - head, B - cross arm, C - ATP binding sites

    (4) A - cross arm, B - head, C - ATP binding sites

    Q58: 88% From NCERT

    Subtopic:  Skeletal Muscle: Myofilaments |

    The action potential that triggers a muscle contraction travels deep within the muscle cell by means of:

    (1) Sarcoplasmic reticulum

    (2) Transverse tubules

    (3) Synapse

    (4) Motor end plates

    Q59:

    Subtopic:  Excitation Contraction Coupling I |

    ATP provides energy for muscle contraction by allowing for:

    (1) An action potential formation in the muscle cell

    (2) Cross-bridge attachment of myosin to actin

    (3) Cross-bridge detachment of myosin from actin

    (4) Release of Ca+2 from sarcoplasmic reticulum

    Q60: From NCERT

    Subtopic:  Energy for Muscle Contraction |

    A motor unit is best described as:

    (1) All the nerve fibres and muscle fibres in a single muscle bundle

    (2) One muscle fibre and its single nerve fibre

    (3) A single motor neuron and all the muscle fibres that it innervates

    (4) It is the neuron which carries the message from muscle to CNS

    Q61: 63% From NCERT

    Subtopic:  Excitation Contraction Coupling I | Excitation Contraction Coupling II | Sliding Filament Theory |

    Electrical excitation in a muscle fibre most directly causes:

    (1) Movement of tropomyosin

    (2) Attachment of the cross bridges to actin

    (3) Release of Ca+2 from sarcoplasmic reticulum

    (4) Splitting of ATP

    Q62: 81% From NCERT

    Subtopic:  Excitation Contraction Coupling I |

    The energy for muscle contraction is most directly obtained from:

    (1) Phosphocreatine (2) ATP

    (3) Anaerobic respiration

    (4) Aerobic respiration

    Q63: 82% From NCERT

    Subtopic:  Energy for Muscle Contraction |

    Put the following phrases in proper order to describe what occurs at the neuromuscular junction to trigger muscle contraction:

    I. Receptor sites on sarcolemma.

    II. Nerve impulse.

    III. Release of Ca+2 from sarcoplasmic reticulum

    IV. The neurotransmitter acetylcholine is released

    V. Sarcomere shortern

    VI. Synaptic cleft

    VII. Spread of impulses over sarcolemma on T-tubules

    (1) II, IV, I, VI, VII, III, V

    (2) II, IV, VI, I, VII, III, V

    (3) I, II, III, IV, V, VI, VII

    (4) VII, VI, V, IV, III, II, I

    Q64: 65% From NCERT

    Subtopic:  Excitation Contraction Coupling I |

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    Source : www.neetprep.com

    Comprehensive Analysis of Tropomyosin Isoforms in Skeletal Muscles by Top

    Mammalian skeletal muscles are heterogeneous in nature and are capable of performing various functions. Tropomyosin (Tpm) is a major component of the thin filament in skeletal muscles and plays an important role in controlling muscle contraction and relaxation. ...

    J Muscle Res Cell Motil. Author manuscript; available in PMC 2017 Apr 18.

    Published in final edited form as:

    J Muscle Res Cell Motil. 2016 Apr; 37(1-2): 41–52.

    Published online 2016 Apr 18. doi: 10.1007/s10974-016-9443-7

    PMCID: PMC4955698

    NIHMSID: NIHMS779712

    PMID: 27090236

    Comprehensive Analysis of Tropomyosin Isoforms in Skeletal Muscles by Top-down Proteomics

    Yutong Jin,a Ying Peng,b,c Ziqing Lin,b,c Yi-Chen Chen,a Liming Wei,b,d Timothy A. Hacker,e Lars Larsson,f and Ying Gea,b,c,*

    Author information Copyright and License information Disclaimer

    The publisher's final edited version of this article is available at J Muscle Res Cell Motil

    See other articles in PMC that cite the published article.

    Associated Data

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    Abstract

    Mammalian skeletal muscles are heterogeneous in nature and are capable of performing various functions. Tropomyosin (Tpm) is a major component of the thin filament in skeletal muscles and plays an important role in controlling muscle contraction and relaxation. Tpm is known to consist of multiple isoforms resulting from different encoding genes and alternative splicing, along with post-translational modifications. However, a systematic characterization of Tpm isoforms in skeletal muscles is still lacking. Therefore, we employed top-down mass spectrometry (MS) to identify and characterize Tpm isoforms present in different skeletal muscles from multiple species, including swine, rat, and human. Our study revealed that Tpm1.1 and Tpm2.2 are the two major Tpm isoforms in swine and rat skeletal muscles, whereas Tpm1.1, Tpm2.2, and Tpm3.12 are present in human skeletal muscles. Tandem MS was utilized to identify the sequences of the major Tpm isoforms. Furthermore, quantitative analysis revealed muscle-type specific differences in the abundance of un-modified and modified Tpm isoforms in rat and human skeletal muscles. This study represents the first systematic investigation of Tpm isoforms in skeletal muscles, which not only demonstrates the capabilities of top-down MS for the comprehensive characterization of skeletal myofilament proteins but also provides the basis for further studies on these Tpm isoforms in muscle-related diseases.

    Keywords: Tropomyosin, Skeletal muscle, Isoform, Post-translational modification, Top-down mass spectrometry

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    Introduction

    Mammalian skeletal muscles are composed of heterogeneous muscle fiber types (Bottinelli and Reggiani 2000; Schiaffino and Reggiani 2011; Scott et al. 2001). This heterogeneity allows skeletal muscles to respond to a variety of functional demands, including sustained low-intensity contractions (e.g. posture keeping), repeated sub-maximal contractions (e.g. locomotion), and high-intensity or maximal contractions (e.g. jumping) (Bottinelli and Reggiani 2000; Schiaffino and Reggiani 2011). Tropomyosin (Tpm) is a major component of the thin filament in skeletal muscles and, as such, plays an important role in the regulation of muscle contraction and relaxation (Gunning et al. 2008; Janco et al. 2013; Rajan et al. 2010). Tpm molecules exist as coiled coil dimers that are assembled head-to-tail to form polymers along the actin thin filament (Schevzov et al. 2005). In the relaxed state, Tpm, along with the troponin complex, blocks the myosin binding sites on the thin filament, preventing cross-bridge formation and, ultimately, muscle contraction (Gunning et al. 2005). However, when the intracellular Ca2+ concentration increases, Ca2+ binding to troponin initiates a conformational change in the Tpm-troponin complex that leads to a azimuthal movement of Tpm along the actin filaments (Hitchcock-DeGregori et al. 1973). This positional shift exposes the myosin-binding sites on the actin filament and allows for cross-bridge formation and muscle contraction.

    The Tpm protein family is known to be highly complex with a myriad isoforms arising from multiple genes (Denz et al. 2004; Perry 2001; Rajan et al. 2010). In total four different genes encode Tpm isoforms, namely TPM1, TPM2, TPM3, and TPM4, each of which gives rise to multiple proteoforms (Smith et al. 2013) via alternative splicing, the selection of alternative promoters, and post-translational modifications (PTMs) (Marston and Redwood 2003; Wieczorek et al. 1988). The TPM1 gene is composed of 15 exons and encodes the greatest number of Tpm isoforms, including Tpm1.1 (also known as Tpm1.1St(a.b.b.a) or α-Tm) (Geeves et al. 2015) expressed in striated muscles and Tpm1.3 present in smooth muscles (Perry 2001). The other major Tpm isoforms expressed in striated and smooth muscles are Tpm2.2 (also known as Tpm2.2St(a.b.b.a) or β-Tm) and Tpm2.1, respectively, which are both encoded by TPM2 (Rajan et al. 2010). Additional Tpm isoforms, including Tpm3.12 (also known as Tpm3.12St(a.b.b.a) or γ-Tm) and Tpm4.1 (also known as Tpm4.1cy(a.b.b.d) or δ-Tpm), are encoded by TPM3 and TPM4, respectively; however, Tpm3.12 is believed to be expressed only in slow-twitch skeletal muscles (Kee and Hardeman 2008; Perry 2001), while Tpm4.1 is detected in both slow and fast twitch muscles (Kee and Hardeman 2008; Wang et al. 2008).

    Given the essential roles of Tpm in regulating muscle contraction, a variety of muscle-related diseases associated with mutations of Tpm encoding gene and expression of Tpm isoforms have been reported (Scellini et al. 2015; Tajsharghi et al. 2012). For example, Memo et al. observed various mutations in Tpm in the actin-Tpm interface and the mutation of amino acids in Tpm can cause a loss-of-function in skeletal muscles (Memo and Marston 2013). In addition, Clarke et al. discovered that the mutation in exon 4 of TPM2 gene which encodes Tpm2.2 is the genetic cause of cap disease (Clarke et al. 2009). Moreover, EI-Mezgueldi et al. demonstrated that the transitions between the inactive and active states of thin filaments are affected by the skeletal muscle myopathy mutations in TPM3 gene of Tpm (El-Mezgueldi et al. 2014). Hence, a systematic assessment of the composition and the relative abundance of Tpm isoforms and their PTMs in skeletal muscles is important but remains lacking.

    Source : www.ncbi.nlm.nih.gov

    Chapter 9: Muscles and Muscle Tissue Flashcards

    Start studying Chapter 9: Muscles and Muscle Tissue. Learn vocabulary, terms, and more with flashcards, games, and other study tools.

    Chapter 9: Muscles and Muscle Tissue

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    What is the role of tropomyosin in skeletal muscles?

    A) Tropomyosin is the name of a contracting unit.

    B) Tropomyosin serves as a contraction inhibitor by blocking the myosin binding sites on the actin molecules.

    C) Tropomyosin serves as a contraction inhibitor by blocking the actin binding sites on the myosin molecules.

    D) Tropomyosin is the receptor for the motor neuron neurotransmitter.

    Click card to see definition 👆

    B) Tropomyosin serves as a contraction inhibitor by blocking the myosin binding sites on the actin molecules.

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    Which muscle cells have the greatest ability to regenerate?

    A) skeletal B) cardiac C) smooth

    D) no muscle can regenerate

    Click card to see definition 👆

    C) smooth

    Click again to see term 👆

    1/56 Created by sinchap94

    Terms in this set (56)

    What is the role of tropomyosin in skeletal muscles?

    A) Tropomyosin is the name of a contracting unit.

    B) Tropomyosin serves as a contraction inhibitor by blocking the myosin binding sites on the actin molecules.

    C) Tropomyosin serves as a contraction inhibitor by blocking the actin binding sites on the myosin molecules.

    D) Tropomyosin is the receptor for the motor neuron neurotransmitter.

    B) Tropomyosin serves as a contraction inhibitor by blocking the myosin binding sites on the actin molecules.

    Which muscle cells have the greatest ability to regenerate?

    A) skeletal B) cardiac C) smooth

    D) no muscle can regenerate

    C) smooth

    Most skeletal muscles contain ________.

    A) muscle fibers of the same type

    B) a mixture of fiber types

    C) a predominance of slow oxidative fibers

    D) a predominance of fast oxidative fibers

    B) a mixture of fiber types

    Fatigued muscle cells that recover rapidly are the products of ________.

    A) intense exercise of long duration

    B) intense exercise of short duration

    C) slow exercise of long duration

    D) slow exercise of short duration

    B) intense exercise of short duration

    The strongest muscle contractions are normally achieved by ________.

    A) increasing stimulus above the threshold

    B) increasing stimulus above the treppe stimulus

    C) increasing the stimulation up to the maximal stimulus

    D) recruiting small and medium muscle fibers

    C) increasing the stimulation up to the maximal stimulus

    Which of the following would be recruited later in muscle stimulation when contractile strength increases?

    A) motor units with the longest muscle fibers

    B) many small motor units with the ability to stimulate other motor units

    C) large motor units with small, highly excitable neurons

    D) motor units with larger, less excitable neurons

    D) motor units with larger, less excitable neurons

    Which of the following is not a usual result of resistance exercise?

    A) increase in the efficiency of the respiratory system

    B) increase in the efficiency of the circulatory system

    C) increase in the number of muscle cells

    D) increase in the number of myofibrils within the muscle cells

    C) increase in the number of muscle cells

    Excitation-contraction coupling requires which of the following substances?

    A) Ca2+ and ATP B) Ca2+ only C) ATP only D) ATP and glucose A) Ca2+ and ATP

    Which of the following is a factor that affects the velocity and duration of muscle

    contraction?

    A) number of muscle fibers stimulated

    B) size of the muscle fibers stimulated

    C) load on the fiber

    D) muscle length

    C) load on the fiber

    Myoglobin ________.

    A) breaks down glycogen

    B) is a protein involved in the direct phosphorylation of ADP

    C) stores oxygen in muscle cells

    D) produces the end plate potential

    C) stores oxygen in muscle cells

    What structure in skeletal muscle cells functions in calcium storage?

    A) sarcoplasmic reticulum

    B) mitochondria

    C) intermediate filament network

    D) myofibrillar network

    A) sarcoplasmic reticulum

    What does oxygen deficit represent?

    A) amount of energy needed for exertion

    B) the difference between the amount of oxygen needed for totally aerobic muscle activity and the amount actually used

    C) the amount of oxygen taken into the body prior to the exertion

    D) the amount of oxygen taken into the body immediately after the exertion

    B) the difference between the amount of oxygen needed for totally aerobic muscle activity and the amount actually used

    Immediately following the arrival of the stimulus at a skeletal muscle cell there is a short period called the ________ period during which the events of excitation-contraction coupling occur.

    A) contraction B) relaxation C) latent D) refractory C) latent

    Creatine phosphate functions in the muscle cell by ________.

    A) forming a temporary chemical compound with myosin

    B) forming a chemical compound with actin

    C) inducing a conformational change in the myofilaments

    D) storing energy that will be transferred to ADP to resynthesize ATP

    D) storing energy that will be transferred to ADP to resynthesize ATP

    What controls the force of muscle contraction?

    Source : quizlet.com

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