1. Typhoid fever in humans is caused by Salmonella typhi and is clinically confirmed by which diagnostic test?
Correct Answer: B (Widal Test)
Salmonella typhi enters the small intestine through contaminated food and water and migrates to other organs. Typhoid is diagnosed serologically using the Widal test.
Salmonella typhi enters the small intestine through contaminated food and water and migrates to other organs. Typhoid is diagnosed serologically using the Widal test.
2. Which characteristic symptom differentiates severe Pneumonia from the Common Cold?
Correct Answer: B (Infection of lung alveoli with fluid accumulation)
Pneumonia (caused by Streptococcus pneumoniae and Haemophilus influenzae) infects the alveoli of the lungs causing fluid filling and impaired gas exchange. Rhinoviruses causing common cold infect the nose and respiratory passage but not the lungs.
Pneumonia (caused by Streptococcus pneumoniae and Haemophilus influenzae) infects the alveoli of the lungs causing fluid filling and impaired gas exchange. Rhinoviruses causing common cold infect the nose and respiratory passage but not the lungs.
3. The infectious stage of Plasmodium that enters the human body through the bite of an infected female Anopheles mosquito is:
Correct Answer: B (Sporozoite)
Sporozoites stored in the salivary glands of the female Anopheles mosquito are inoculated into the human bloodstream during a bite and initially travel to liver cells.
Sporozoites stored in the salivary glands of the female Anopheles mosquito are inoculated into the human bloodstream during a bite and initially travel to liver cells.
4. The recurring chills and high fever associated with malaria are caused by the release of which toxic substance upon the rupture of red blood cells?
Correct Answer: B (Haemozoin)
Rupture of erythrocytic schizonts releases merozoites along with a toxic byproduct called haemozoin, which induces a recurring chill and high fever every 3 to 4 days.
Rupture of erythrocytic schizonts releases merozoites along with a toxic byproduct called haemozoin, which induces a recurring chill and high fever every 3 to 4 days.
5. Which species of Plasmodium is responsible for malignant, often fatal cerebral malaria?
Correct Answer: D (Plasmodium falciparum)
Malignant tertian malaria caused by Plasmodium falciparum is the most severe and life-threatening form of human malaria.
Malignant tertian malaria caused by Plasmodium falciparum is the most severe and life-threatening form of human malaria.
6. Amoebic dysentery (Amoebiasis) is caused by the protozoan parasite Entamoeba histolytica. What serves as its principal mechanical carrier?
Correct Answer: B (Housefly)
Houseflies act as mechanical carriers, transmitting parasites from the feces of infected persons to water and food supplies, leading to infection of the large intestine.
Houseflies act as mechanical carriers, transmitting parasites from the feces of infected persons to water and food supplies, leading to infection of the large intestine.
7. Ascariasis is characterized by internal bleeding, muscular pain, fever, anemia, and intestinal blockage. How is it transmitted?
Correct Answer: B (Ingestion of contaminated food and water)
Ascaris lumbricoides eggs are excreted along with the feces of infected individuals, contaminating soil, water, and crops.
Ascaris lumbricoides eggs are excreted along with the feces of infected individuals, contaminating soil, water, and crops.
8. Chronic inflammation and gross deformities of the lower limbs and genital organs in Elephantiasis (Filariasis) are caused by:
Correct Answer: A (Wuchereria bancrofti and Wuchereria malayi)
Filarial worms (Wuchereria) reside in the lymphatic vessels of the lower limbs for years, causing chronic lymphatic obstruction and swelling. The pathogen is transmitted by female Culex mosquitoes.
Filarial worms (Wuchereria) reside in the lymphatic vessels of the lower limbs for years, causing chronic lymphatic obstruction and swelling. The pathogen is transmitted by female Culex mosquitoes.
9. Ringworm infection in humans, characterized by dry, scaly lesions with intense itching on skin, nails, and scalp, is caused by fungi belonging to the genera:
Correct Answer: B (Microsporum, Trichophyton, and Epidermophyton)
These dermatophytes thrive in warm, moist body folds (such as groin or between toes), producing spreading, scaly circular lesions.
These dermatophytes thrive in warm, moist body folds (such as groin or between toes), producing spreading, scaly circular lesions.
10. Both Dengue fever and Chikungunya are viral vector-borne diseases transmitted to humans by:
Correct Answer: C (Aedes aegypti mosquitoes)
Aedes mosquitoes are day-biting vectors that transmit both Dengue and Chikungunya viruses in tropical and subtropical regions.
Aedes mosquitoes are day-biting vectors that transmit both Dengue and Chikungunya viruses in tropical and subtropical regions.
11. Which of the following is categorized as a physiological barrier in innate immunity?
Correct Answer: B (Acid in stomach, saliva, and tears)
Skin/mucus are physical barriers; PMNL/macrophages are cellular barriers; interferons are cytokine barriers; gastric acid, saliva, and tears represent physiological barriers.
Skin/mucus are physical barriers; PMNL/macrophages are cellular barriers; interferons are cytokine barriers; gastric acid, saliva, and tears represent physiological barriers.
12. Interferons are cytokine proteins secreted by virus-infected cells that function by:
Correct Answer: B (Protecting non-infected surrounding cells)
Interferons induce antiviral proteins in neighboring cells, inhibiting viral replication and preventing the spread of infection.
Interferons induce antiviral proteins in neighboring cells, inhibiting viral replication and preventing the spread of infection.
13. An antibody molecule is represented structurally as H2L2 because it contains:
Correct Answer: B (Two heavy and two light polypeptide chains)
Each antibody monomer consists of 4 polypeptide chains: 2 long heavy (H) chains and 2 short light (L) chains connected by disulfide bonds.
Each antibody monomer consists of 4 polypeptide chains: 2 long heavy (H) chains and 2 short light (L) chains connected by disulfide bonds.
14. Which antibody class is predominantly found in colostrum, providing natural passive immunity to newborns?
Correct Answer: B (IgA)
Secretory IgA antibodies are abundantly present in mother’s colostrum, coating the infant’s gut to provide crucial localized passive immunity.
Secretory IgA antibodies are abundantly present in mother’s colostrum, coating the infant’s gut to provide crucial localized passive immunity.
15. Allergic reactions (such as hay fever and asthma) involve the release of histamine and serotonin from mast cells, mediated primarily by which antibody?
Correct Answer: D (IgE)
Allergens bind to IgE antibodies attached to the surface of tissue mast cells, triggering degranulation and the rapid release of histamine and serotonin.
Allergens bind to IgE antibodies attached to the surface of tissue mast cells, triggering degranulation and the rapid release of histamine and serotonin.
16. Which of the following is a classic example of an autoimmune disease in humans?
Correct Answer: B (Rheumatoid arthritis)
In rheumatoid arthritis, the body loses self-tolerance; the immune system produces autoantibodies against its own joint tissues and synovial membranes.
In rheumatoid arthritis, the body loses self-tolerance; the immune system produces autoantibodies against its own joint tissues and synovial membranes.
17. Which of the following organs are classified as primary lymphoid organs where immature lymphocytes differentiate and mature into antigen-sensitive lymphocytes?
Correct Answer: B (Bone marrow and Thymus)
Primary lymphoid organs provide microenvironments for the maturation of B-cells (in bone marrow) and T-cells (in thymus). Secondary lymphoid organs (spleen, lymph nodes) are sites of antigen interaction.
Primary lymphoid organs provide microenvironments for the maturation of B-cells (in bone marrow) and T-cells (in thymus). Secondary lymphoid organs (spleen, lymph nodes) are sites of antigen interaction.
18. Mucosa-Associated Lymphoid Tissue (MALT) constitutes approximately what percentage of all lymphoid tissue in the human body?
Correct Answer: C (50%)
MALT is located within the lining of the respiratory, digestive, and urogenital tracts and accounts for about 50% of the body’s total lymphoid tissue.
MALT is located within the lining of the respiratory, digestive, and urogenital tracts and accounts for about 50% of the body’s total lymphoid tissue.
19. The Human Immunodeficiency Virus (HIV) primarily invades and destroys which critical immune cells, causing severe immunodeficiency?
Correct Answer: B (Helper T-lymphocytes)
HIV replicates inside helper T cells (CD4+), lysing them and causing a progressive decrease in CD4+ cell counts, leaving patients vulnerable to opportunistic infections (like Mycobacterium, Toxoplasma, and fungi).
HIV replicates inside helper T cells (CD4+), lysing them and causing a progressive decrease in CD4+ cell counts, leaving patients vulnerable to opportunistic infections (like Mycobacterium, Toxoplasma, and fungi).
20. What is the standard preliminary screening test used for the detection of HIV antibodies?
Correct Answer: A (ELISA)
ELISA is widely employed as the primary serological screening test for HIV infection, with positive results confirmed by Western Blot analysis.
ELISA is widely employed as the primary serological screening test for HIV infection, with positive results confirmed by Western Blot analysis.
21. Normal cells exhibit a property called contact inhibition, which prevents uncontrolled growth. Cancerous cells:
Correct Answer: B (Lose contact inhibition)
Cancer cells lose contact inhibition, allowing them to proliferate continuously over neighboring cells, resulting in neoplastic tumor masses.
Cancer cells lose contact inhibition, allowing them to proliferate continuously over neighboring cells, resulting in neoplastic tumor masses.
22. The most feared biological characteristic of malignant tumors, in which cancerous cells slough off and establish secondary tumors at distant sites via blood or lymph, is called:
Correct Answer: C (Metastasis)
Metastasis is the spread of malignant tumor cells from the primary site to distant tissues, making cancer management and treatment challenging.
Metastasis is the spread of malignant tumor cells from the primary site to distant tissues, making cancer management and treatment challenging.
23. In cancer immunotherapy, patients are administered alpha-interferon as a biological response modifier to:
Correct Answer: B (Activate the patient’s immune system)
Tumor cells often evade immune detection; biological response modifiers like alpha-interferon stimulate host immune surveillance to target and destroy tumors.
Tumor cells often evade immune detection; biological response modifiers like alpha-interferon stimulate host immune surveillance to target and destroy tumors.
24. Heroin (commonly known as “smack”) is chemically synthesized by:
Correct Answer: A (Acetylation of morphine)
Heroin is a white, odorless, bitter crystalline compound produced by the diacetylation of morphine extracted from the latex of the opium poppy (Papaver somniferum).
Heroin is a white, odorless, bitter crystalline compound produced by the diacetylation of morphine extracted from the latex of the opium poppy (Papaver somniferum).
25. Cannabinoids (marijuana, hashish, charas, ganja) extracted from Cannabis sativa interact with cannabinoid receptors in the brain and primarily affect the:
Correct Answer: B (Cardiovascular system of the body)
Cannabinoids interact with specific receptors located predominantly in the brain and have prominent stimulating effects on the cardiovascular system.
Cannabinoids interact with specific receptors located predominantly in the brain and have prominent stimulating effects on the cardiovascular system.
26. Cocaine (coke or crack), an alkaloid derived from the South American plant Erythroxylum coca, produces euphoria and high energy by interfering with the transport of:
Correct Answer: B (Dopamine)
Cocaine blocks the reuptake of the neurotransmitter dopamine at synaptic clefts, causing prolonged stimulation of the central nervous system and intense euphoria.
Cocaine blocks the reuptake of the neurotransmitter dopamine at synaptic clefts, causing prolonged stimulation of the central nervous system and intense euphoria.
27. Which of the following plants possess well-known hallucinogenic properties that are frequently abused?
Correct Answer: B (Atropa belladonna and Datura)
Atropa belladonna and Datura contain tropane alkaloids (like scopolamine and atropine) with potent hallucinogenic and anticholinergic effects.
Atropa belladonna and Datura contain tropane alkaloids (like scopolamine and atropine) with potent hallucinogenic and anticholinergic effects.
28. Tobacco smoking stimulates adrenal glands to release adrenaline and noradrenaline into the bloodstream, raising blood pressure and heart rate, due to the alkaloid:
Correct Answer: C (Nicotine)
Tobacco contains nicotine, which stimulates nicotinic acetylcholine receptors in the adrenal medulla, triggering the release of catecholamines (adrenaline/noradrenaline).
Tobacco contains nicotine, which stimulates nicotinic acetylcholine receptors in the adrenal medulla, triggering the release of catecholamines (adrenaline/noradrenaline).
29. Chronic and excessive intake of alcohol over an extended duration severely damages the liver, leading to:
Correct Answer: A (Cirrhosis of liver)
Chronic alcoholism leads to progressive fatty liver, hepatitis, and irreversible scarring (fibrosis) of hepatic parenchyma known as cirrhosis.
Chronic alcoholism leads to progressive fatty liver, hepatitis, and irreversible scarring (fibrosis) of hepatic parenchyma known as cirrhosis.
30. Tobacco smoke contains high levels of Carbon Monoxide (CO), which is harmful because it:
Correct Answer: B (Binds strongly to hemoglobin)
CO has ~200 times higher affinity for hemoglobin than oxygen, forming carboxyhemoglobin and reducing oxygen delivery to body tissues.
CO has ~200 times higher affinity for hemoglobin than oxygen, forming carboxyhemoglobin and reducing oxygen delivery to body tissues.
31. Lactic Acid Bacteria (LAB) convert milk into curd, improving its nutritional quality by increasing the concentration of:
Correct Answer: C (Vitamin B12)
LAB (like Lactobacillus) ferment milk sugars into lactic acid, coagulating milk proteins and enriching curd with Vitamin B12 while suppressing harmful gut microbes.
LAB (like Lactobacillus) ferment milk sugars into lactic acid, coagulating milk proteins and enriching curd with Vitamin B12 while suppressing harmful gut microbes.
32. The puffed-up appearance of dough used for making bread, idli, and dosa is caused by the release of:
Correct Answer: C (Carbon dioxide)
Baker’s yeast (Saccharomyces cerevisiae) ferments sugars anaerobically, releasing CO2 bubbles that get trapped and cause the dough to swell and rise.
Baker’s yeast (Saccharomyces cerevisiae) ferments sugars anaerobically, releasing CO2 bubbles that get trapped and cause the dough to swell and rise.
33. The characteristic large holes in “Swiss Cheese” are produced by the bacterium:
Correct Answer: B (Propionibacterium sharmanii)
Propionibacterium sharmanii produces large amounts of CO2 during fermentation, creating large holes within Swiss cheese.
Propionibacterium sharmanii produces large amounts of CO2 during fermentation, creating large holes within Swiss cheese.
34. Roquefort cheese is ripened to attain a specific flavor by growing which microorganism on it?
Correct Answer: C (Specific fungi (Penicillium roqueforti))
Roquefort cheese is aged with Penicillium roqueforti mold, which hydrolyzes fats and proteins to yield its distinct flavor and blue-green marbling.
Roquefort cheese is aged with Penicillium roqueforti mold, which hydrolyzes fats and proteins to yield its distinct flavor and blue-green marbling.
35. “Toddy”, a traditional fermented beverage of parts of Southern India, is made by fermenting:
Correct Answer: B (Sap extracted from palm trees)
Toddy is produced through natural fermentation of sugary sap tapped from the inflorescence of palm trees by wild yeasts.
Toddy is produced through natural fermentation of sugary sap tapped from the inflorescence of palm trees by wild yeasts.
36. The first commercially isolated antibiotic, Penicillin, was discovered serendipitously by Alexander Fleming while working on:
Correct Answer: C (Staphylococci bacteria)
Fleming observed that a mold (Penicillium notatum) contaminating a Staphylococci culture plate produced a chemical inhibiting bacterial growth. Its full potential was later developed by Howard Florey and Ernst Chain.
Fleming observed that a mold (Penicillium notatum) contaminating a Staphylococci culture plate produced a chemical inhibiting bacterial growth. Its full potential was later developed by Howard Florey and Ernst Chain.
37. Which of the following matched pairs correctly links the organic acid to its microbial producer?
Correct Answer: B (Citric acid – Aspergillus niger)
Aspergillus niger produces Citric acid; Acetobacter aceti produces Acetic acid; Clostridium butylicum produces Butyric acid; and Lactobacillus produces Lactic acid.
Aspergillus niger produces Citric acid; Acetobacter aceti produces Acetic acid; Clostridium butylicum produces Butyric acid; and Lactobacillus produces Lactic acid.
38. Which enzyme produced by Streptococcus bacteria and modified by genetic engineering is used clinically as a “clot buster” for clearing blood clots in myocardial infarction patients?
Correct Answer: C (Streptokinase)
Streptokinase acts as a thrombolytic agent (clot buster) by activating plasminogen to dissolve intravascular fibrin clots in heart attack patients.
Streptokinase acts as a thrombolytic agent (clot buster) by activating plasminogen to dissolve intravascular fibrin clots in heart attack patients.
39. Bottled fruit juices bought from the market are clearer than home-made fresh juices because commercial juices are clarified using:
Correct Answer: A (Pectinases and Proteases)
Pectinases and proteases break down insoluble plant cell-wall pectins and proteins, eliminating haze and clarifying commercial fruit juices.
Pectinases and proteases break down insoluble plant cell-wall pectins and proteins, eliminating haze and clarifying commercial fruit juices.
40. Cyclosporin A, an important immunosuppressive agent used in organ transplant patients, is commercially produced from the fungus:
Correct Answer: B (Trichoderma polysporum)
Trichoderma polysporum produces Cyclosporin A, a cyclic non-ribosomal peptide that selectively inhibits T-cell activation to prevent graft rejection.
Trichoderma polysporum produces Cyclosporin A, a cyclic non-ribosomal peptide that selectively inhibits T-cell activation to prevent graft rejection.
41. Statins, used as blood-cholesterol lowering agents by competitively inhibiting the enzyme responsible for cholesterol synthesis, are extracted from the yeast:
Correct Answer: B (Monascus purpureus)
Statins produced by the yeast Monascus purpureus competitively inhibit HMG-CoA reductase, the rate-limiting enzyme in cholesterol biosynthesis.
Statins produced by the yeast Monascus purpureus competitively inhibit HMG-CoA reductase, the rate-limiting enzyme in cholesterol biosynthesis.
42. In sewage water treatment, the primary treatment stage is fundamentally a:
Correct Answer: B (Physical process)
Primary sewage treatment physically removes floating debris via sequential wire-mesh filtration and settles out grit/solids in primary settling tanks.
Primary sewage treatment physically removes floating debris via sequential wire-mesh filtration and settles out grit/solids in primary settling tanks.
43. During secondary (biological) sewage treatment, vigorous aeration promotes the rapid growth of “flocs”. What are flocs?
Correct Answer: B (Masses of aerobic bacteria with fungal filaments)
Flocs consist of aerobic bacteria enmeshed in fungal hyphae. They consume dissolved organic matter in aeration tanks, reducing wastewater BOD.
Flocs consist of aerobic bacteria enmeshed in fungal hyphae. They consume dissolved organic matter in aeration tanks, reducing wastewater BOD.
44. Biochemical Oxygen Demand (BOD) serves as a direct indicator of water pollution. A higher BOD level indicates that the water sample:
Correct Answer: B (Has high organic matter and greater polluting potential)
BOD measures the amount of oxygen required by microorganisms to oxidize organic matter in 1 liter of water. High BOD reflects high organic waste load.
BOD measures the amount of oxygen required by microorganisms to oxidize organic matter in 1 liter of water. High BOD reflects high organic waste load.
45. In anaerobic sludge digesters during wastewater treatment, methanogenic bacteria digest sludge and produce a mixture of gases known as biogas, containing primarily:
Correct Answer: A (CH4, H2S, and CO2)
Anaerobic methanogens digest aerobic flocs in anaerobic sludge digesters, generating inflammable biogas composed mostly of methane, carbon dioxide, and hydrogen sulfide.
Anaerobic methanogens digest aerobic flocs in anaerobic sludge digesters, generating inflammable biogas composed mostly of methane, carbon dioxide, and hydrogen sulfide.
46. The bacterium Methanobacterium used in rural biogas (Gobar gas) plants is commonly found in:
Correct Answer: B (Anaerobic sludge and rumen of cattle)
Methanobacterium thrives in anaerobic conditions such as the rumen of ruminant livestock, where it digests cellulose, making dung (gobar) rich in methanogens.
Methanobacterium thrives in anaerobic conditions such as the rumen of ruminant livestock, where it digests cellulose, making dung (gobar) rich in methanogens.
47. Bacillus thuringiensis (Bt) strains are widely utilized as microbial biocontrol agents against:
Correct Answer: B (Insect pests, particularly butterfly caterpillars)
Dried spores of Bt mixed with water and sprayed on crops are ingested by insect larvae; the protoxin activates in the alkaline larval midgut, creating pores and killing the caterpillar.
Dried spores of Bt mixed with water and sprayed on crops are ingested by insect larvae; the protoxin activates in the alkaline larval midgut, creating pores and killing the caterpillar.
48. The free-living fungus Trichoderma is widely used as an effective biological control agent against:
Correct Answer: B (Several soil-borne fungal plant pathogens)
Trichoderma species are common free-living fungi in the root ecosystem (rhizosphere) that antagonize and suppress root pathogens through mycoparasitism and antibiosis.
Trichoderma species are common free-living fungi in the root ecosystem (rhizosphere) that antagonize and suppress root pathogens through mycoparasitism and antibiosis.
49. Baculoviruses belonging to the genus Nucleopolyhedrovirus (NPV) are excellent biological control agents for Integrated Pest Management (IPM) programs because they:
Correct Answer: B (Species-specific, narrow-spectrum agents)
Baculoviruses target specific arthropods without harming plants, mammals, birds, fish, or non-target beneficial insects, making them ideal for IPM.
Baculoviruses target specific arthropods without harming plants, mammals, birds, fish, or non-target beneficial insects, making them ideal for IPM.
50. Mycorrhiza, a symbiotic association between fungi (e.g., genus Glomus) and higher plant roots, benefits the host plant primarily by:
Correct Answer: B (Absorbing phosphorus and conferring stress tolerance)
The fungal symbiont absorbs phosphorus from soil and passes it to the plant, while conferring enhanced tolerance to drought, salinity, and root pathogens.
The fungal symbiont absorbs phosphorus from soil and passes it to the plant, while conferring enhanced tolerance to drought, salinity, and root pathogens.