Bio 242 Final Exam Practice Questions with Correct
Verified answers/ Latest .
1. A single skeletal muscle cell is known as a:
• A. Myofibril
• B. Sarcomere
• C. Muscle fiber
• D. Myofilament
Correct Answer: C
Rationale: A single skeletal muscle cell is called a muscle fiber.
These are long, multinucleated cells that contain myofibrils
composed of sarcomeres, which are the functional contractile units.
Myofibrils are bundles of myofilaments within the muscle fiber .
2. Thick filaments within the myofibril are composed of which
protein?
• A. Actin
1
, • B. Myosin
• C. Tropomyosin
• D. Troponin
Correct Answer: B
Rationale: Thick filaments are composed of the protein myosin.
Myosin molecules have globular heads that form cross-bridges with
actin thin filaments during contraction. Actin is the primary protein
of thin filaments. Tropomyosin and troponin are regulatory proteins
associated with thin filaments .
3. Which organelle stores calcium within the muscle fiber?
• A. Sarcoplasmic reticulum
• B. T-tubules
• C. Mitochondria
• D. Golgi apparatus
Correct Answer: A
Rationale: The sarcoplasmic reticulum is a modified endoplasmic
2
,reticulum that stores calcium ions and surrounds each myofibril.
Lateral sacs of the sarcoplasmic reticulum store calcium, which is
released during excitation-contraction coupling .
4. When calcium binds to troponin, what occurs?
• A. Myosin heads detach from actin
• B. Tropomyosin shifts, exposing myosin-binding sites on actin
• C. The sarcomere relaxes
• D. ATP is consumed
Correct Answer: B
Rationale: When calcium binds to troponin, the shape of this
protein changes, causing tropomyosin to slide away from its
blocking position. This exposes the myosin-binding sites on actin,
allowing cross-bridge formation and muscle contraction .
5. What is the correct sequence of events in excitation-
contraction coupling?
3
, 1. Tropomyosin shifts and unblocks myosin-binding sites
2. Calcium is released and binds to troponin complex
3. Transverse tubules depolarize the sarcoplasmic reticulum
4. Thin filaments are pulled across thick filaments by myosin
heads using ATP
5. Action potential in motor neuron releases ACh, depolarizing
the muscle cell membrane
• A. 5, 3, 2, 1, 4
• B. 3, 2, 5, 1, 4
• C. 5, 2, 3, 1, 4
• D. 1, 2, 3, 4, 5
Correct Answer: A
Rationale: The correct sequence is: (5) Action potential in motor
neuron → ACh release → muscle cell depolarization; (3) T-tubules
depolarize SR; (2) Calcium is released and binds troponin; (1)
4
Verified answers/ Latest .
1. A single skeletal muscle cell is known as a:
• A. Myofibril
• B. Sarcomere
• C. Muscle fiber
• D. Myofilament
Correct Answer: C
Rationale: A single skeletal muscle cell is called a muscle fiber.
These are long, multinucleated cells that contain myofibrils
composed of sarcomeres, which are the functional contractile units.
Myofibrils are bundles of myofilaments within the muscle fiber .
2. Thick filaments within the myofibril are composed of which
protein?
• A. Actin
1
, • B. Myosin
• C. Tropomyosin
• D. Troponin
Correct Answer: B
Rationale: Thick filaments are composed of the protein myosin.
Myosin molecules have globular heads that form cross-bridges with
actin thin filaments during contraction. Actin is the primary protein
of thin filaments. Tropomyosin and troponin are regulatory proteins
associated with thin filaments .
3. Which organelle stores calcium within the muscle fiber?
• A. Sarcoplasmic reticulum
• B. T-tubules
• C. Mitochondria
• D. Golgi apparatus
Correct Answer: A
Rationale: The sarcoplasmic reticulum is a modified endoplasmic
2
,reticulum that stores calcium ions and surrounds each myofibril.
Lateral sacs of the sarcoplasmic reticulum store calcium, which is
released during excitation-contraction coupling .
4. When calcium binds to troponin, what occurs?
• A. Myosin heads detach from actin
• B. Tropomyosin shifts, exposing myosin-binding sites on actin
• C. The sarcomere relaxes
• D. ATP is consumed
Correct Answer: B
Rationale: When calcium binds to troponin, the shape of this
protein changes, causing tropomyosin to slide away from its
blocking position. This exposes the myosin-binding sites on actin,
allowing cross-bridge formation and muscle contraction .
5. What is the correct sequence of events in excitation-
contraction coupling?
3
, 1. Tropomyosin shifts and unblocks myosin-binding sites
2. Calcium is released and binds to troponin complex
3. Transverse tubules depolarize the sarcoplasmic reticulum
4. Thin filaments are pulled across thick filaments by myosin
heads using ATP
5. Action potential in motor neuron releases ACh, depolarizing
the muscle cell membrane
• A. 5, 3, 2, 1, 4
• B. 3, 2, 5, 1, 4
• C. 5, 2, 3, 1, 4
• D. 1, 2, 3, 4, 5
Correct Answer: A
Rationale: The correct sequence is: (5) Action potential in motor
neuron → ACh release → muscle cell depolarization; (3) T-tubules
depolarize SR; (2) Calcium is released and binds troponin; (1)
4
