All Free Biology MCQs with Answers

3131. Which of the following will be curable in the next two decades?

• A. Tuberculosis
• B. Cancer
• C. Poliomyelitis
• D. Aging

Explanation: Cancer may be curable in the next two decades. The completion of the human genome is causing profound changes in the thinking and direction of biomedical research. Cancer is caused by the malfunctioning of genes, either through the activation of cancer-causing oncogenes or through the inactivation of tumor suppressor genes. By comparing the active genes in the tumor to those of normal cells, the genes causing the cancer can be determined. Side by side, there is significant progress in the fields of genetic engineering and biotechnology. All these aspects give us hope that cancer may be curable in the next two decades. Tuberculosis is curable by taking antitubercular drugs, and polio may be on the verge of eradication if the pulse polio program succeeds. Aging is a natural biological process, not a disease.

3132. The protein coat of a virus enclosing nucleic acid is called the:

• A. Vector
• B. Capsid
• C. Plasmid
• D. Genome

Explanation: A capsid is a protective protein shell made up of subunits called capsomeres, which are arranged in highly specific patterns that determine the overall shape of the virus (helical, icosahedral, or complex). Its main function is to safeguard the viral genetic material (DNA or RNA) from physical damage, enzymatic degradation, and recognition by the host immune system. In addition, the capsid plays an essential role in the infection process, as it helps the virus attach to host cells and facilitates the delivery of nucleic acid into the host. In some viruses, the capsid is further surrounded by an outer lipid membrane called the envelope, but the capsid itself is a universal feature of all viruses.

3133. Carbon dioxide released by respiration just equals the quantity required by photosynthesizing cells. This is termed:

• A. Bacteriochlorophylls
• B. Redox process
• C. Photosystems
• D. Compensation point

Explanation: The compensation point is when the rate of photosynthesis matches the rate of respiration, resulting in no net gas exchange because carbon dioxide and oxygen needs are internally balanced.

3134. FADH2 is produced during:

• A. Glycolysis
• B. The oxidation of pyruvate
• C. Krebs cycle
• D. None of these.

Explanation: The Krebs cycle, occurring in the mitochondrial matrix, is where FADH is produced as a result of the oxidation of acetyl-CoA.

3135. NADH is oxidized by:

• A. Co-enzyme Q
• B. Cytochrome b
• C. Cytochrome c
• D. Cytochrome a

Explanation: NADH is oxidized by Coenzyme Q. This oxidation yields enough free energy to permit the synthesis of a molecule of ATP from ADP and inorganic phosphate.

3136. The electron transport chain occurs in:

• A. Inner membrane of mitochondria
• B. Outer membrane of mitochondria
• C. Thylakoid membrane
• D. Both A and C

Explanation: The electron transport chain is located in the inner mitochondrial membrane. The inner membrane is highly folded to form structures called cristae, providing a large surface area for the enzymes and protein complexes involved in oxidative phosphorylation.

3137. A process that uses membranes to couple redox reactions to ATP production is termed:

• A. Chemiosmosis
• B. ATP Synthase
• C. Dark reactions
• D. Light reactions

Explanation: Chemiosmosis is the process in which the flow of electrons through the photosynthetic pathway pumps protons across the thylakoid membrane, creating a proton gradient that drives ATP synthesis.

3138. The terminal cytochrome of the respiratory chain, which donates electrons to oxygen, is:

• A. Cytochrome b
• B. Cytochrome c
• C. Cytochrome a3
• D. Cytochrome a1

Explanation: Cytochrome a is a subunit of cytochrome c oxidase, which is the terminal complex (complex IV) in the electron transport chain. Cytochrome a directly transfers electrons to oxygen, reducing it to water.

3139. Exchange of the respiratory gases between organism and environment is termed as:

• A. Cell Respiration
• B. Glycolysis
• C. External respiration
• D. Alcoholic fermentation

Explanation: External respiration involves the exchange of respiratory gases (oxygen and carbon dioxide) between the organism and the external environment, typically occurring in the lungs or gills.

3140. The first step in glycolysis is the transfer of the phosphate group from ATP to glucose. Which product is formed by this reaction?

• A. Fructose-1-phosphate
• B. Glucose-6-Phosphate
• C. Fructose-6-phosphate
• D. Fructose-1,6-bisphosphate

Explanation: This is the direct product formed when a phosphate group is transferred from ATP to Glucose 6 phosphate in the first step of glycolysis.