Statement I :
Myofibrils are not attached to the plasma membrane.

Statement II :
Myofibrils are attached to the plasma membrane at both ends of a muscle fibre.

In the light of the above statements, choose the
correct answer from the options given below :

1. Both Statement I and Statement II are true
2. Both Statement I and Statement II are false
3. Statement I is true but Statement II is false
4. Statement I is false but Statement II is true

   Answer: Both Statement I and Statement II are false.​

   Myofibrils are contractile structures within skeletal muscle fibers that run parallel to the fiber’s length. They are indeed attached to the plasma membrane (sarcolemma), contradicting both statements.

   Statement Analysis

   Statement I (False): Myofibrils are attached to the plasma membrane. They connect at their ends to the sarcolemma, enabling force transmission during contraction, so the claim of no attachment is incorrect.

   Statement II (False): While myofibrils attach to the sarcolemma, this occurs primarily at the ends via myotendinous junctions (one end per fiber in typical models), not “at both ends of a muscle fibre.” Muscle fibers align in series, with attachments at fiber termini, not bilaterally per myofibril.

   Option Breakdown

   • Both true: Incorrect, as attachments exist and “both ends” misstates anatomy.

   • Both false: Correct—Statement I denies proven attachments; Statement II overstates endpoint specificity.​

   • I true, II false: Incorrect, since I is false.

   • I false, II true: Incorrect, since II is false.

   Myofibrils attachment to plasma membrane is a key topic in muscle physiology for biology students preparing for competitive exams. This article breaks down two statements on myofibrils in muscle fibres, explaining why myofibrils are linked to the sarcolemma (plasma membrane) and clarifying endpoint attachments.

   Understanding Myofibrils in Muscle Fibers

   Myofibrils are longitudinal bundles inside each muscle fiber, comprising sarcomeres for contraction. The plasma membrane, or sarcolemma, envelops the fiber, with myofibrils spanning its length and anchoring at ends for force transfer.​

   Evaluating Statement I

   “Myofibrils are not attached to the plasma membrane.”
   This is false. Myofibrils attach to the sarcolemma at termini, allowing synchronized shortening of the fiber during contraction.

   Evaluating Statement II

   “Myofibrils are attached to the plasma membrane at both ends of a muscle fibre.”
   False due to imprecise wording. Attachments occur at fiber ends (myotendinous junctions), but not symmetrically “at both ends” per individual fiber in standard skeletal muscle.

   Correct Option Explained

   Both Statement I and Statement II are false. This resolves common exam confusion on myofibril-sarcolemma interactions.​

   Exam Tips for Muscle Fiber Questions

   • Recall: Sarcolemma = plasma membrane; myofibrils attach for contraction.

   • Visualize: Myofibrils parallel to fiber axis, end-anchored.​

   • Practice similar MCQs on sarcomeres and sarcoplasmic reticulum.