All Free Biology MCQs with Answers

• A. Sarcomere
• B. Sarcoplasmic reticulum
• C. Sarcoplasm
• D. Sarcolemma

Explanation: A sarcomere is the fundamental structural and functional unit of a muscle.

• A. Haemoglobin
• B. Actin
• C. Myoglobin
• D. Myosin

Explanation: Myosin is the protein that constitutes the thick filaments in a myofibril.

• A. Sarcolemma
• B. Sarcoplasm
• C. Plasma membrane
• D. Myofibrils

Explanation: The sarcolemma is the specialized cell membrane of a muscle fiber (muscle cell).

• A. Actin
• B. Myosin
• C. Troponin
• D. Tropomyosin

Explanation: Actin is a protein that makes up the thin filaments in muscle fibers. Actin is composed of globular monomers known as G-actin (globular…

• A. Actin
• B. Myosin
• C. Troponin
• D. Tropomyosin

Explanation: Actin has 2 polypeptide chains. Myosin has 6 polypetides. Tropomyosin has 2 polypeptides. Troponin has 3 chains.

• A. Troponin and tropomyosin
• B. Actin filaments and myosin heads
• C. Calcium and sodium
• D. Sarcolemma and sarcoplasmic reticulum

Explanation: Cross bridges form between actin filaments and myosin heads. During muscle contraction, myosin heads attach to binding sites on actin…

• A. Tropomyosin
• B. Tubulin
• C. Troponin
• D. Sarcomere

Explanation: When a muscle is at rest, tropomyosin is a regulatory protein that covers the myosin-binding sites on the actin filament.

• A. I band shortens
• B. A band remains unchanged
• C. Z-lines get closer
• D. M-line disappears

Explanation: During muscle contraction, I-Band shortens, Z-lines get closer to each other and H-zone disappears. A-Band and M-line remain unchanged.

• A. Actin
• B. Myosin
• C. Troponin
• D. Tropomyosin

Explanation: Myosin is a contractile protein found in muscle cells, and it contains ATPase activity.

• A. Formation of actin-myosin cross bridges
• B. An action potential
• C. Sarcomere contraction
• D. An increase in calcium ion concentration

Explanation: An action potential, which is an electrical signal generated by nerve cells, triggers the release of calcium ions from the sarcoplasmic…

• A. I-bands shorten
• B. Z-lines move further apart
• C. H-zone becomes more visible
• D. A-bands shorten

Explanation: According to sliding filament model of muscle contraction, the following changes can occur Z-lines come brought closer together.I-band…

• A. All the muscle fibers within a given muscle
• B. A motor neuron and the muscle fibers it innervates
• C. All the neurons going into an individual section of a body
• D. A fascicle and a nerve

Explanation: A motor unit is indeed composed of a motor neuron and all the muscle fibers it innervates (connects to).

• A. ATP
• B. Phosphocreatine
• C. Fatty acids
• D. Glycogen

Explanation: ATP is the immediate source of energy for muscle contraction. Adenosine triphosphate (ATP) is a molecule found in cells that serves as a…

• A. Overlapping
• B. Shortening
• C. Lengthening
• D. Contraction

Explanation: During muscle contraction, the thick (myosin) and thin (actin) filaments undergo overlapping.

• A. Smooth muscles
• B. Skeletal muscles
• C. Cardiac muscles
• D. Involuntary muscles

Explanation: Skeletal muscles are the muscles that are attached to the skeleton through tendons.

• A. Ligament
• B. Belly
• C. Tendon
• D. Smooth muscle

Explanation: Option C is correct. A tendon is a bundle of collagen fibers that attach muscle to bone.

• A. Muscle fibre
• B. Cardiac fibre
• C. Muscle bundles
• D. Myofilament

Explanation: Option A is correct.A muscle fiber is a long, cylindrical cell that is the basic unit of skeletal muscle tissue.

• A. Large amount of stored starch
• B. A unique oxygen binding protein, myoglobin
• C. Hemoglobin that stores oxygen
• D. Large amount of stored lipids

Explanation: Option B is correct.Myoglobin is an oxygen-binding protein that is found in the sarcoplasm of muscle fibers.

• A. Muscle bundle
• B. Tendon
• C. Muscle fibre or muscle cell
• D. Myofilament

Explanation: Option B is correct.Myofibrils are long, cylindrical structures that run parallel to each other in the muscle fiber.

• A. Neurolemma
• B. Nuclear membrane
• C. Sarcoplasmic reticulum
• D. Muscle cell membrane or sarcolemma

Explanation: Option D is correct.The muscle cell membrane is also known as the sarcolemma. It is the plasma membrane that surrounds a muscle fiber.