All Free Biology MCQs with Answers

• A. Kidney
• B. Liver
• C. Heart
• D. Stomach

Explanation: Cardiac Muscle is an involuntary striated muscle tissue found only in the heart and is responsible for the ability of the heart to pump…

• A. Intestinal muscles
• B. Triceps
• C. Biceps
• D. Triceps and biceps

Explanation: The striated appearance of skeletal muscle tissue is a result of repeating bands of the proteins actin and myosin that are present along…

• A. Myosin only
• B. Actin only
• C. Both actin and myosin
• D. Actin, myosin and tropomyosin

Explanation: Actin, Myosin and tropomyosin are the major structural and regulatory proteins present in the skeletal muscles.

• A. They are multinucleated.
• B. They are 1-1 nm in diameter and surrounded by sarcolemma.
• C. They contain O2 storing molecules called myoglobin.
• D. Their cytoplasm contains the high concentration of carbohydrates .

Explanation: Skeletal muscle fibres are not 1-1 nm in diameter. They are 10-100 micrometer in diameter and are surrounded by sarcolemma.

• A. They are linked together via intercalated discs.
• B. There are gap junctions between cells.
• C. They form branching chains.
• D. They are non-striated.

Explanation: Cardiac muscle (also called heart muscle or myocardium) is one of three types of vertebrate muscle tissue, with the other two being…

• A. I band
• B. H zone
• C. A band
• D. Z disc

Explanation: Z-discs are the dividing points between sarcomeres. Actin filaments extend from this region and are joined together by several complex…

• A. Skeletal muscle
• B. Cardiac muscle
• C. Smooth muscle
• D. Both B and C

Explanation: Smooth muscles are uni-nucleated and non-striated. It is composed of small spindle-shaped cells with a single, central nucleus.

• A. ATP does all of these things during muscle contraction.
• B. It allows the myosin head to detach from the actin filament.
• C. It moves tropomyosin off of actin binding sites.
• D. Both A and B

Explanation: Energy from ATP is required for the myosin head to release from the actin filament-otherwise the myosin heads would remain in the same…

• A. Striated muscle
• B. Smooth muscle
• C. Cardiac muscle
• D. Skeletal muscle

Explanation: Smooth muscle fibers are nonstriated, spindle-shaped and have 1 nucleus per cell.

• A. Skeletal: striated, voluntary
• B. Cardiac: striated, involuntary
• C. Cardiac: striated, voluntary
• D. Both B and C

Explanation: Correct Option is C as cardiac muscles are involuntary.

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

Explanation: At high magnification, small bridge-like structures can be seen on the thick filaments (myosin) extending toward the thin filaments…

• A. Striated and branched
• B. Multinucleated
• C. Self excitatory
• D. None of these

Explanation: Each cardiac myocyte contains a single, centrally located nucleus and is surrounded by a cell membrane known as the sarcolemma.

• A. Regulation of ion concentration
• B. Muscular contraction
• C. Organ and nerve protection
• D. Regulation of pH through hydration

Explanation: Muscular contraction is not a direct function of bones. Muscular contraction is a function of the muscles themselves.

• A. Two
• B. One
• C. Three
• D. Four

Explanation: The actin molecules contain active sites, to which myosin heads will bind, during contraction.

• A. Bind to troponin molecule and cause them to move
• B. Polarize visible light
• C. Aid in the transmission of nerve impulse
• D. Bind to tropomyosin molecule and cause them to form cross bridges

Explanation: Calcium ions play a critical role in muscle contraction by binding to the troponin molecules present on the thin filaments.

• A. I band
• B. H zone
• C. A band
• D. None of these

Explanation: Even though the 'I band' and the 'H zone' change in length, the 'A band' remains the same in length.

• A. Osteocytes
• B. Osteoclasts
• C. Chondrocytes
• D. Osteoblasts

Explanation: 'Chondrocytes' are the first chondroblast cells that produce the collagen extracellular matrix (ECM) and then get caught in the matrix.

• A. Microtubules
• B. Myofibril
• C. Myosin filament
• D. M-line

Explanation: The subunits of a 'myofibril' are sarcomeres.

• A. T-tubule
• B. Sarcomere
• C. Myoplasmic reticulum
• D. Sarcoplasmic reticulum

Explanation: The sarcoplasmic reticulum (SR) is a membrane-bound structure found within muscle cells that is similar to the smooth endoplasmic…

• A. Actin filament
• B. Sarcomere
• C. Both Options A and B are correct
• D. Myosin

Explanation: Option A: Actin filament alone does not shorten during muscle contraction.