All Free Biology MCQs with Answers

• A. Arginine
• B. Valine
• C. Glutamic acid
• D. Tryptophan

Explanation: In mitochondria UGA codon is assigned to tryptophan (Trp) instead of being a signal for translational termination.

• A. DNA ligase
• B. DNA polymerase
• C. Ribosomes
• D. RNA polymerase

Explanation: Transcription has three stages: initiation, elongation, and termination.

• A. Mononucleotide
• B. Dinucleotide
• C. Tri nucleotide
• D. Tetra nucleotide

Explanation: Nicotinamide adenine dinucleotide (NAD) is a cofactor central to metabolism.

• A. Cell membrane
• B. Cytoplasm
• C. Nucleolus
• D. Lysosomes

Explanation: The nucleolus is the site of the highest RNA synthesis rate in cell nuclei giving rise to more than 60% of the entire RNA pool.

• A. Na+ ions
• B. Mg++ ions
• C. Ca·++ ion
• D. K+ ions

Explanation: Ribosomes are composed of two subunits known as large and small, which unites to form the active ribosome during the process of protein…

• A. Mononucleotide
• B. Dinucleotide
• C. Trinucleotide
• D. Tetranucleotide

Explanation: Nicotinamide adenine dinucleotide (NAD) is a cofactor central to metabolism.

• A. Double helical structure
• B. Ribose sugar
• C. Thymine
• D. Sugar - phosphate backbone

Explanation: As we can see that the double-helical structure and the nitrogenous base Thymine are exclusive to DNA, while RNA solely posses the Ribose…

• A. Syphilis
• B. Gonorrhea
• C. Genital herpes
• D. Both A and C
• E. None of the above

Explanation: Explanation for this question will be added soon.

• A. Hepatitis A
• B. Hepatitis B
• C. Hepatitis C
• D. Hepatitis D

Explanation: Hepatitis B (HBV) is the second major form of hepatitis. It is caused by a DNA virus that is very common in Asia, China, the Philippines…

• A. Pox virus
• B. Influenza virus
• C. Herpes virus
• D. Flu virus

Explanation: Herpes is an infection that is caused by a herpes simplex virus (HSV). Oral herpes causes cold sores around the mouth or face.

• A. HSV-1
• B. HSV-2
• C. Both A and B
• D. None of these

Explanation: Genital herpes is an STD caused by herpes simplex virus type 2 (HSV-2). So, option B is correct.

• A. HSV-1
• B. HSV-2
• C. Both A and B
• D. None of these

Explanation: Genital herpes is a common sexually transmitted infection caused by the herpes simplex virus (HSV-2).

• A. Activation of killer T lymphocytes by infected cells
• B. Cloning of B lymphocytes to form plasma cells
• C. Ingestion of a bacterial cell by a neutrophil
• D. Presentation of antigen on the cell surface of macrophages

Explanation: c) Ingestion of a bacterial cell by a neutrophil:This option describes a non-specific immune response.

• A. A chemical that causes muscle hypertrophy
• B. A bacteria
• C. A foreign substance that produces an immune response
• D. A substance that causes a monocyte to transform into a macrophage
• E. A substance that agglutinates bacteria and marks them for phagocytosis

Explanation: Explanation for this question will be added soon.

• A. Self against antigens
• B. Antigen against self
• C. Self against self
• D. Antigen destroyed

Explanation: Autoimmune disease occurs when a specific adaptive immune response is mounted against self antigens.

• A. Belong to cytokines
• B. Activate natural killer cells
• C. Activate immune cells
• D. Secrete interleukin

Explanation: Interferons (IFNs) are a broad class of cytokines that are part of your natural defenses.

• A. Interfere with pathogenic colonization
• B. Develop resistance against antigens
• C. Develop resistance against physical agents
• D. Produce antibiotic against pathogens

Explanation: Bacterial flora is beneficial because it prevents colonisation by pathogens by competing for attachment & nutrients.

• A. Radiotherapy
• B. Chemotherapy
• C. Vaccination
• D. Antibiotics

Explanation: Acquired immunity comes from vaccines and exposure to diseases. These enable the body to develop antigens that can help it fight the same…

• A. Neutralizing an antigen
• B. Precipitating an antigen
• C. Secreting cytokines
• D. Enhancing phagocytosis

Explanation: Antibody cells do not secrete many cytokines upon activation.

• A. Neutralizing an antigen
• B. Precipitating an antigen
• C. Secretion of cytokines
• D. Enhancing phagocytosis

Explanation: Antibodies primarily work by neutralizing antigens, precipitating antigens, and enhancing phagocytosis.