All Free Biology MCQs with Answers

• A. Avoiding intravenous drugs
• B. Avoiding intracellular drugs
• C. Avoiding use of syringes
• D. Avoiding direct contact with HIV

Explanation: The most important measure to prevent AIDS and HIV is avoiding direct contact with HIV.

• A. 2
• B. 3
• C. 4
• D. 1

Explanation: Each HIV virion contains two molecules of reverse transcriptase. This enzyme is essential for converting the viral RNA genome into…

• A. The core, or tube, is made up of distinct proteins
• B. The core or tube is enclosed in a sheath
• C. The core and sheath are made of the same type of protein
• D. The Core and Sheath are made of another type of protein

Explanation: The answer is "Core and sheath are made of the same type of protein."Explanation: The core of the tail is made up of a rigid and…

• A. 1
• B. 10
• C. 100
• D. 1000

Explanation: The volume of the T4 phage is about one-thousandth (1/1000th) of the volume of its bacterial host, E. coli.

• A. Louis Pasteur and Charles Chamberland
• B. Ivanowsky
• C. Louis Pasteur and W.M. Stanley
• D. Louis Pasteur and Robert Koch

Explanation: The correct answer is Louis Pasteur and Robert Koch. During the late 19th century, the term 'virus' was primarily used to describe…

• A. AIDS is an immunodeficiency disease.
• B. It is caused by the retrovirus HIV.
• C. HIV selectively infects and kills B-lymphocytes.
• D. Retroviruses have RNA genomes that replicate a DNA intermediates.

Explanation: HIV (Human Immunodeficiency Virus) is a retrovirus that primarily targets the immune system, leading to immune deficiency.

• A. Viruses possess their own metabolic system
• B. Viruses contain either DNA or RNA
• C. Viruses are facultative parasites
• D. Viruses are readily killed by antibiotics

Explanation: The correct statement about viruses is that they contain either DNA or RNA as their genetic material, but never both, which is essential…

• A. DNA molecules without a protein coat.
• B. RNA molecules with a protein coat.
• C. RNA molecules without a protein coat.
• D. DNA molecules with a protein coat.

Explanation: RNA molecules without a protein coat: This is the correct description of viroids.

• A. Integrase
• B. Protease
• C. Reverse transcriptase
• D. DNA polymerase

Explanation: The integration of HIV DNA into the host's DNA is performed by the viral enzyme integrase.

• A. Blood transfusion
• B. Sexual contact
• C. Breastfeeding
• D. Mosquito bite

Explanation: HIV spreads through blood transfusion, unprotected sexual contact, and breastfeeding, but not through mosquito bites.

• A. Musca domestica-a common reptile
• B. Plasmodium falciparum-a protozoan pathogen causing the most serious type of malaria.
• C. Felis tigris-the Indian tiger, well protected in Gir forests
• D. E. coli-full name Entamoeba coli, a commonly occurring bacterium in the human intestine

Explanation: Plasmodium falciparum is a protozoan parasite and the most dangerous cause of malaria in humans.

• A. Binomial nomenclature
• B. Theory of biogenesis
• C. Discovery of microscope
• D. Evolution through natural selection

Explanation: Binomial nomenclature of scientific naming was first given by C. Linnaeus (1735) in his book Systema Naturae and later in "Species…

• A. Species
• B. Kingdom
• C. Family
• D. Order

Explanation: The basic unit or smallest taxon of taxonomy/classification is species.

• A. Prophage
• B. Provirus
• C. Bacteriophage
• D. Virions

Explanation: A provirus and a virion are not the entities that specifically affect bacteria because they refer to general stages or forms of viruses…

• A. DNA to RNA
• B. RNA to DNA
• C. DNA to proteins
• D. RNA to proteins

Explanation: Reverse transcriptase is a key enzyme in certain viruses, such as retroviruses, which include HIV.

• A. Glucose
• B. Pyruvate
• C. Acetyl CoA
• D. CO2

Explanation: Glycolysis converts glucose to 2 pyruvate molecules, with net gain of 2 ATP and 2 NADH.

• A. Alcoholic fermentation
• B. Lactic acid fermentation
• C. Aerobic respiration
• D. None of these

Explanation: Aerobic respiration is the process where glucose is completely broken down in the presence of oxygen.

• A. 0.3%
• B. 0.03-0.04
• C. 3%
• D. 30%

Explanation: The concentration of carbon dioxide in air is approximately 0.03-0.04%.

• A. Leaves respire utilizing O2 and releasing CO2
• B. Photosynthesis and respiration occur at the same rate, resulting in no net exchange of gases between the atmosphere and plants
• C. The rate of photosynthesis increases, resulting in a net release of oxygen and uptake of CO2
• D. The rate of respiration exceeds the rate of photosynthesis, resulting in a net release of carbon dioxide

Explanation: The compensation point is a specific condition in plant physiology where the rates of photosynthesis and respiration are equal.

• A. Glucose-6-phosphate
• B. Fructose-6-phosphate
• C. Pyruvate
• D. 3-Phosphoglycerate
• E. Phosphoglyceraldehyde

Explanation: The end product of glycolysis is pyruvate. During glycolysis, one molecule of glucose is broken down into two molecules of pyruvate…