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The myosin myofilament can be cleaved in...

The myosin myofilament can be cleaved into a head and a tail piece. All of the following are accurate in describing the position of myosin in a sacromere except
(i) A-band is the length of a myosin myoilaments
(ii) A-band contains thin and thick myofilaments
(iii) A-band does not include actin-binding sites

A

I and II only

B

II and III only

C

III only

D

I, II and III

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The correct Answer is:
To solve the question regarding the position of myosin in a sarcomere, we need to analyze each of the given statements about the A-band in the context of muscle anatomy. ### Step-by-Step Solution: 1. **Understanding the Sarcomere Structure**: - A sarcomere is the basic contractile unit of muscle fibers. It consists of thick (myosin) and thin (actin) filaments. 2. **Analyzing the Statements**: - **Statement (i)**: "A-band is the length of a myosin myofilament." - The A-band does indeed contain the length of the myosin filaments, but it also includes overlapping regions of actin filaments. Therefore, this statement is **incorrect** as it does not fully account for the presence of actin in the A-band. - **Statement (ii)**: "A-band contains thin and thick myofilaments." - This statement is **correct**. The A-band is composed of both thick (myosin) and thin (actin) filaments, as they overlap in this region. - **Statement (iii)**: "A-band does not include actin-binding sites." - This statement is **incorrect**. The A-band includes myosin, which has actin-binding sites that allow for muscle contraction. Therefore, this statement is also not accurate. 3. **Identifying the Incorrect Statement**: - The question asks for the statement that is **not accurate**. Both statements (i) and (iii) are incorrect. However, since we need to choose one, we can conclude that statement (i) is the primary focus as it misrepresents the A-band as solely myosin. ### Conclusion: The answer to the question is that the statement which is not accurate in describing the position of myosin in a sarcomere is: - **(i) A-band is the length of a myosin myofilament.**
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Explain how any change in the A, H and I band lengths are brought about in terms of what happens to the actin and myosin filaments.

Read the given Statements for skeletal muscles (i) Thin filaments are firmly attached to the Z - line . (ii) The light band is also called the I - band and contains mostly actin. (iii) A sarcomere is the functional unit of a myofibril between two adjacent A - bands . (iv) The central part of the thick filament , not overlapped by the thick filament is called the H - zone Which of these is/are CORRECT ?

Statements A-bands of the muscle are dark and contain myosin I-band are the light bands and contain action During muscle contration the A-band contracts The part between the two Z-lines is called as saromere The central part of thin filament, not over-lapped by thick filament is called H-zone of the above statements.

Read the following statements and select the correct option : I. In the skeletal muscles fibre, large number of myofilaments are arranged in the sarcoplasm. II. The central part of an anisotropic band where the only thick , filament is present and thin filament is absent is called 'A' band. III. In the resting state , a tropomyosin protein masks the active b binding sites for myosin on the active filaments . IV. The junction between a motor neuron and the sarcolemma of the muscle fibres is called motor-end plate.

Which of the following statements about the molecular arrangement of actin and mysin In myofibre is/are incorrect ? (i) Each actin (thin filament) is made of 2F (filamentous) actins. (ii) F-actin is the polymer of G (globular) actin. (iii) 2F0actins are twisted into a helix. (iv) Two strands of tropomyosin (protein) lie in the grooves of F-actin. (v) Troponin molecules (complex proteins) are distributed at regular intervals on the tropomyosin. (vi) Troponin forms the head of the myosin molecule. (vii) The myosin is a polymerised protein.

Which of the following statements are correct regarding muscle proteins ? (i) Actin is a thin filament and is mde up to two F-actin (ii) The complex protein, tropomyosin is distributed at regular intervals on the troponin (iii) Myosin is a thick filament which is also a polymerised protein. (iv) The globular head of meromyosin consists of light meromyosin (LMM).

The steps involved in the mechanism of muscle contraction are given below. Arrange the steps in proper sequential order and select the correct option. I. Release of calcium ions in the sarcoplasm. II. Signal sent by the CNS via a motor neuron. III. Binding of calcium with a subunit of troponin on actin filaments. IV. Generation of the action potential in the sarcolemma. V. Binding of myosin head to the exposed active sites on actin to form a cross-bridge. VI. Inward pulling of ‘Z’ line attached to actin causing shortening of the sarcomere. VII. Pulling of the attached actin filaments towards the centre of 'A' band. VIII. Release of neurotransmitter acetylcholine and generation of the action potential in the sarcolemma.

Select the total number of false statement from the following (i) The globular head is an active ATPase enzyme and has binding sites for ATP and active sites for Myosin. (ii) Each Myosin filament is also a polymerized protein (iii) Many monomeric proteins celled Meromyosins constitute one thick filament. (iv) Each meromyosin has two important parts, a globular head with a short arm and a tail, the former being called the heavy meromyosin (HMA) and the latter, the light meromysin (LMN). (v) The HMM component, i.e., the head and short arm projects outwards at regular distance and angle from each other from the surface of a polymerized myosin filament and is known as cross arm (a) 5 (b) 4 (c) 2 (d)1

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