All Free Biology MCQs with Answers

• A. Macrophages
• B. Lymphocytes
• C. Blood cells
• D. Skin

Explanation: The correct answer is skin. The skin acts as a physical barrier, preventing harmful pathogens from entering the body.

• A. C-cells
• B. A & B cells
• C. B & C cells
• D. B & T cells

Explanation: The most abundant lymphocytes are B and T cells, which play critical roles in the immune system.

• A. Attenuated vaccine
• B. Killed vaccine
• C. Subunit vaccine
• D. Toxoid vaccine

Explanation: Killed vaccine has least side effect. An inactivated vaccine (or killed vaccine) is a vaccine consisting of virus particles, bacteria, or…

• A. Sebum
• B. Perspiration
• C. Interferon
• D. Epidermis

Explanation: The first line of defense includes physical and chemical barriers like the skin (including the epidermis), sebum, and perspiration, which…

• A. Platelets
• B. Cytotoxic T cells
• C. Antigens
• D. Red blood cell

Explanation: Cytotoxic T cells are a type of T lymphocyte that specifically targets and kills cells displaying foreign motifs on their surface.

• A. Inactivated vaccine
• B. Toxoid vaccine
• C. Subunit vaccine
• D. Live, attenuated vaccine

Explanation: Toxoid vaccines, such as those for diphtheria and tetanus, contain inactivated toxins produced by bacteria.

• A. Eosinophils
• B. Basophils
• C. Neusrophils
• D. Lymphocytes

Explanation: The most common form of white blood cells (WBCs) in the body are neutrophils.

• A. Lung cancer
• B. Tuberculosis
• C. Pneumonia
• D. Emphysema

Explanation: Option B, "Tuberculosis," is the correct answer. The BCG (Bacillus Calmette-Guérin) vaccine is primarily used for the prevention of…

• A. Natural killer cell
• B. Macrophages
• C. Antibodies
• D. Neutrophils

Explanation: Neutrophils are the first responders - they rush to the infection site, attack bacteria, and die in large numbers.During healing…

• A. Platelets
• B. Eosinophils
• C. B-Lymphocytes
• D. T-Lymphocytes

Explanation: The thymus gland is a primary lymphoid organ responsible for the maturation and development of T-lymphocytes (T cells).

• A. Directly kill invaders
• B. Aid B cells in their job
• C. Both a and b
• D. Suppress T cell activity

Explanation: Cytotoxic T-cells (also known as CD8+ T-cells) are a type of immune cell that directly kill infected cells, cancer cells, or cells that…

• A. Most abundant form of WBC's
• B. Have a short life span.
• C. Made by the thymus gland.
• D. Released by the bone marrow.

Explanation: Neutrophils are not made by the thymus gland. The thymus gland is responsible for the maturation and development of T-lymphocytes (a type…

• A. It is produced at the site of tissue injury.
• B. It has no role in the leakage of fluids into the tissues in inflammation.
• C. It destroys phagocytes.
• D. It produces interferon gamma.

Explanation: Bradykinin is a peptide hormone that plays a key role in the inflammatory response.

• A. rRNA
• B. mRNA
• C. DNA
• D. Nucleotides

Explanation: A DNA molecule is a double helix carrying the genetic information of an organism.

• A. CACGTC
• B. TAGCATG
• C. TACGAG
• D. GACGTG

Explanation: In DNA, the base pairs are complementary to each other. Adenine (A) always pairs with thymine (T), and guanine (G) always pairs with…

• A. Parallel
• B. Antiparallel
• C. ......
• D. None

Explanation: Each strand has a backbone made up of alternating sugars and phosphate groups.

• A. Cytosine
• B. Adenine
• C. Uracil
• D. Thymine

Explanation: Purines, such as adenine and guanine, have a double-ringed structure - one hexagonal pyrimidine ring and an imidazole ring.

• A. AUAGA
• B. ATACA
• C. UAUGU
• D. ATACT

Explanation: Nucleotides are the building blocks of nucleic acids, i.e., DNA and RNA.

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

Explanation: RNA (Ribonucleic Acid) and DNA (Deoxyribonucleic Acid) differ in their sugar components.

• A. Interphase
• B. Prophase
• C. Metaphase
• D. Anaphase

Explanation: The correct answer is Interphase. During interphase, the cell prepares for division, and the DNA in the nucleus replicates.