2-3 Questions
Avg NEET Questions/Year
8-12 Marks
Weightage Impact
30 MCQs
Question Bank Size
Key Focus Areas: Household/Industrial microbes, Sewage treatment, Biogas, Biocontrol agents, Biofertilizers.
Complete Microbes in Human Welfare Question Bank & Solutions (30 Questions)
Q1 of 30
NEET NCERT Line-by-Line
Lactic Acid Bacteria (LAB) check the growth of disease-causing microbes in the stomach and increase:
(A)
Vitamin B1
(B)
Vitamin B12
(C)
Vitamin C
(D)
Vitamin D
Show Answer & NCERT Explanation
Correct Answer: (B) Vitamin B12
LAB grows in milk and converts it to curd, digesting casein and enriching the curd with Vitamin B12, which is essential for human health.
Q2 of 30
NEET NCERT Line-by-Line
Which of the following organic acids is produced by a fungal microbe?
(A)
Acetic acid
(B)
Citric acid
(C)
Butyric acid
(D)
Lactic acid
Show Answer & NCERT Explanation
Correct Answer: (B) Citric acid
Citric acid is produced by Aspergillus niger, which is a fungus. Acetic acid (Acetobacter), butyric acid (Clostridium), and lactic acid (Lactobacillus) are produced by bacteria.
Q3 of 30
NEET NCERT Line-by-Line
Which enzyme is clinically referred to as a 'clot buster'?
(A)
Lipase
(B)
Pectinase
(C)
Streptokinase
(D)
Amylase
Show Answer & NCERT Explanation
Correct Answer: (C) Streptokinase
Streptokinase, produced by Streptococcus, is genetically engineered to serve as a clot buster, dissolving blood clots in patients with heart attacks.
Q4 of 30
NEET NCERT Line-by-Line
BOD is a measure of:
(A)
Inorganic minerals in sewage
(B)
Pathogenic load in water
(C)
Organic matter in water
(D)
Dissolved oxygen in aeration tank
Show Answer & NCERT Explanation
Correct Answer: (C) Organic matter in water
BOD (Biochemical Oxygen Demand) measures the amount of oxygen required by bacteria to decompose the organic matter present in a water sample. It is a direct indicator of organic pollution levels.
Q5 of 30
NEET NCERT Line-by-Line
During anaerobic digestion of sewage sludge, which mixture of gases is produced?
(A)
Methane, Oxygen, CO2
(B)
Methane, Hydrogen Sulfide, CO2
(C)
Ethane, Hydrogen Sulfide, CO2
(D)
Methane, Nitrogen, Oxygen
Show Answer & NCERT Explanation
Correct Answer: (B) Methane, Hydrogen Sulfide, CO2
Anaerobic sludge digesters host bacteria that digest organic mass, producing biogas, which is composed of Methane (CH4), Hydrogen Sulfide (H2S), and Carbon dioxide (CO2).
Q6 of 30
NEET NCERT Line-by-Line
The Bt toxin is activated in the caterpillar's gut due to:
(A)
Acidic pH
(B)
Neutral pH
(C)
Alkaline pH
(D)
High temperature
Show Answer & NCERT Explanation
Correct Answer: (C) Alkaline pH
Bt toxin is ingested as an inactive protoxin. It is solubilised and activated in the alkaline pH of the insect's midgut, leading to cell lysis.
Q7 of 30
NEET NCERT Line-by-Line
Baculoviruses used as biocontrol agents belong to the genus:
(A)
Glomus
(B)
Nucleopolyhedrovirus
(C)
Trichoderma
(D)
Methanobacterium
Show Answer & NCERT Explanation
Correct Answer: (B) Nucleopolyhedrovirus
Baculoviruses used for narrow-spectrum biological control belong to the genus Nucleopolyhedrovirus, targeting specific insect families.
Q8 of 30
NEET NCERT Line-by-Line
Fungi of the genus Glomus form symbiotic associations to absorb which mineral?
(A)
Nitrogen
(B)
Phosphorus
(C)
Potassium
(D)
Iron
Show Answer & NCERT Explanation
Correct Answer: (B) Phosphorus
Mycorrhizal fungi of the genus Glomus absorb phosphorus from soil minerals and transfer it to the host plant.
Q9 of 30
NEET NCERT Line-by-Line
Which yeast is used as baker's yeast for fermenting bread dough?
(A)
Saccharomyces lactis
(B)
Saccharomyces cerevisiae
(C)
Candida albicans
(D)
Aspergillus oryzae
Show Answer & NCERT Explanation
Correct Answer: (B) Saccharomyces cerevisiae
Baker's yeast is Saccharomyces cerevisiae. It ferments the sugars in dough, releasing CO2 which causes the dough to rise.
Q10 of 30
NEET NCERT Line-by-Line
Roquefort cheese gets its distinct flavour due to ripening by:
(A)
Propionibacterium sharmanii
(B)
Lactobacillus lactis
(C)
A specific fungus grown on it
(D)
Aspergillus niger
Show Answer & NCERT Explanation
Correct Answer: (C) A specific fungus grown on it
Roquefort cheese is ripened by growing a specific fungus on it, which gives it a characteristic flavour and bluish appearance.
Q11 of 30
NEET NCERT Line-by-Line
Which of the following beverages are produced WITHOUT distillation of the fermented broth?
(A)
Whisky and Rum
(B)
Brandy and Rum
(C)
Wine and Beer
(D)
Vodka and Gin
Show Answer & NCERT Explanation
Correct Answer: (C) Wine and Beer
Wine and Beer are produced by fermenting malted cereals or fruit juices without distillation. Whisky, Brandy, and Rum require distillation.
Q12 of 30
NEET NCERT Line-by-Line
Penicillin was discovered by Alexander Fleming from which organism?
(A)
Penicillium chrysogenum
(B)
Penicillium notatum
(C)
Aspergillus fumigatus
(D)
Streptomyces griseus
Show Answer & NCERT Explanation
Correct Answer: (B) Penicillium notatum
Alexander Fleming discovered penicillin in 1928 when he noticed the mould Penicillium notatum killing Staphylococcus bacteria on his petri dish.
Q13 of 30
NEET NCERT Line-by-Line
Who established the full potential of penicillin as an effective antibiotic and received the Nobel Prize?
(A)
Pasteur and Koch
(B)
Chain and Florey
(C)
Fleming and Chain
(D)
Florey and Fleming
Show Answer & NCERT Explanation
Correct Answer: (B) Chain and Florey
Ernest Chain and Howard Florey established the full potential of penicillin and received the Nobel Prize in 1945 along with Alexander Fleming.
Q14 of 30
NEET NCERT Line-by-Line
Cyclosporin A, used as an immunosuppressant, is produced by:
(A)
Monascus purpureus
(B)
Trichoderma polysporum
(C)
Streptococcus
(D)
Aspergillus niger
Show Answer & NCERT Explanation
Correct Answer: (B) Trichoderma polysporum
Cyclosporin A is a bioactive molecule produced by the fungus Trichoderma polysporum and is used as an immunosuppressant in organ-transplant patients.
Q15 of 30
NEET NCERT Line-by-Line
Statins, used to lower blood cholesterol, are produced by:
(A)
Yeast Monascus purpureus
(B)
Bacterium Streptomyces
(C)
Fungus Aspergillus fumigatus
(D)
Bacterium Clostridium
Show Answer & NCERT Explanation
Correct Answer: (A) Yeast Monascus purpureus
Statins are produced by the yeast Monascus purpureus. They inhibit the enzyme responsible for cholesterol synthesis (competitive inhibitor) and are widely used to control blood cholesterol.
Q16 of 30
NEET NCERT Line-by-Line
Flocs in the aeration tank of a sewage treatment plant are made of:
(A)
Only bacteria
(B)
Only fungi
(C)
Bacteria and fungal filaments
(D)
Algae and protozoa
Show Answer & NCERT Explanation
Correct Answer: (C) Bacteria and fungal filaments
Flocs are mesh-like structures formed by the association of aerobic bacteria and fungal filaments. They digest and absorb the organic matter in the sewage, reducing BOD.
Q17 of 30
NEET NCERT Line-by-Line
What is the biochemical oxygen demand (BOD) a measure of?
(A)
The amount of oxygen in the air above water
(B)
The amount of organic matter in water
(C)
The number of bacteria per litre
(D)
The pH of the water sample
Show Answer & NCERT Explanation
Correct Answer: (B) The amount of organic matter in water
BOD refers to the amount of oxygen required by bacteria to completely oxidise the organic matter present in one litre of water. More BOD = more organic pollution.
Q18 of 30
NEET NCERT Line-by-Line
After primary sewage treatment, the effluent is called:
(A)
Biogas
(B)
Activated sludge
(C)
Primary effluent
(D)
Clarified water
Show Answer & NCERT Explanation
Correct Answer: (C) Primary effluent
After primary treatment (large filtration + sedimentation to remove floating and settable solids), the resulting liquid is called primary effluent, which then undergoes secondary treatment.
Q19 of 30
NEET NCERT Line-by-Line
Biogas mainly contains which gas?
(A)
Hydrogen
(B)
Nitrogen
(C)
Methane
(D)
Carbon dioxide
Show Answer & NCERT Explanation
Correct Answer: (C) Methane
Biogas is predominantly composed of methane (CH4), along with H2S and CO2, produced by the anaerobic digestion of sludge by methanogens.
Q20 of 30
NEET NCERT Line-by-Line
Mycorrhizae are associations between plants and:
(A)
Cyanobacteria
(B)
Fungi
(C)
Rhizobium bacteria
(D)
Viruses
Show Answer & NCERT Explanation
Correct Answer: (B) Fungi
Mycorrhizae are mutualistic associations between plant roots and fungi (like Glomus). The fungal hyphae enhance the plant's nutrient absorption, especially phosphorus.
Q21 of 30
NEET NCERT Line-by-Line
Which of the following is an example of a free-living nitrogen-fixer?
(A)
Rhizobium
(B)
Trichoderma
(C)
Anabaena
(D)
Glomus
Show Answer & NCERT Explanation
Correct Answer: (C) Anabaena
Anabaena (a cyanobacterium) is a free-living nitrogen fixer found in soil. Rhizobium is a symbiotic nitrogen fixer (lives in legume root nodules).
Q22 of 30
NEET NCERT Line-by-Line
Which microbe is an example of a symbiotic nitrogen-fixing bacterium?
(A)
Azospirillum
(B)
Clostridium
(C)
Rhizobium
(D)
Nostoc
Show Answer & NCERT Explanation
Correct Answer: (C) Rhizobium
Rhizobium lives symbiotically in root nodules of leguminous plants and fixes atmospheric nitrogen into a usable form for the plant.
Q23 of 30
NEET NCERT Line-by-Line
The biological control agent Trichoderma is used against:
(A)
Nematodes
(B)
Caterpillar pests
(C)
Several plant pathogens
(D)
Aphids only
Show Answer & NCERT Explanation
Correct Answer: (C) Several plant pathogens
Trichoderma species are free-living fungi that are effective biocontrol agents against several plant pathogens (fungi).
Q24 of 30
NEET NCERT Line-by-Line
Baculoviruses are used as biocontrol agents primarily because they:
(A)
Attack a wide range of insects
(B)
Are narrow-spectrum and attack only specific insects
(C)
Are chemical pesticides
(D)
Kill all soil fungi
Show Answer & NCERT Explanation
Correct Answer: (B) Are narrow-spectrum and attack only specific insects
Baculoviruses are species-specific and are narrow-spectrum, making them excellent biocontrol agents — they kill only the target pest and do not affect other organisms.
Q25 of 30
NEET NCERT Line-by-Line
Which pollen of which plant is used in Integrated Pest Management?
(A)
Weed that attracts aphids
(B)
Ladybird beetles
(C)
Dragonfly larvae
(D)
Nucleopolyhedrovirus
Show Answer & NCERT Explanation
Correct Answer: (D) Nucleopolyhedrovirus
Nucleopolyhedrovirus (a Baculovirus) is used as a biocontrol agent in Integrated Pest Management (IPM) programmes.
Q26 of 30
NEET NCERT Line-by-Line
Bioactive molecule Statin works by:
(A)
Blocking fat absorption in intestine
(B)
Competitive inhibition of cholesterol-synthesizing enzyme
(C)
Destroying LDL particles
(D)
Increasing HDL production
Show Answer & NCERT Explanation
Correct Answer: (B) Competitive inhibition of cholesterol-synthesizing enzyme
Statins competitively inhibit the enzyme HMG-CoA reductase, which is responsible for the synthesis of cholesterol in the liver.
Q27 of 30
NEET NCERT Line-by-Line
Which organism is responsible for large holes in Swiss cheese?
(A)
Lactobacillus acidophilus
(B)
Penicillium camemberti
(C)
Propionibacterium sharmanii
(D)
Aspergillus flavus
Show Answer & NCERT Explanation
Correct Answer: (C) Propionibacterium sharmanii
Propionibacterium sharmanii produces large amounts of CO2 during cheese ripening, which gets trapped and forms the large holes characteristic of Swiss cheese.
Q28 of 30
NEET NCERT Line-by-Line
Lactic acid bacteria (LAB) improve human health by:
(A)
Producing Vitamin C
(B)
Producing Vitamin B12
(C)
Inhibiting fat absorption
(D)
Producing antibiotics
Show Answer & NCERT Explanation
Correct Answer: (B) Producing Vitamin B12
LAB in curd improve its nutritional quality by producing Vitamin B12. They also check disease-causing microbes in the stomach.
Q29 of 30
NEET NCERT Line-by-Line
Which enzyme produced by bacteria is used as a clot buster in heart attack patients?
(A)
Lipase from Aspergillus
(B)
Amylase from Bacillus
(C)
Streptokinase from Streptococcus
(D)
Pectinase from Pseudomonas
Show Answer & NCERT Explanation
Correct Answer: (C) Streptokinase from Streptococcus
Streptokinase is produced by Streptococcus bacteria. It dissolves blood clots and is used as a 'clot buster' in treating heart attack patients.
Q30 of 30
NEET NCERT Line-by-Line
Which of the following correctly describes the sequence of sewage treatment stages?
(A)
Secondary → Primary → Tertiary
(B)
Tertiary → Primary → Secondary
(C)
Primary → Secondary → Tertiary
(D)
Primary → Tertiary → Secondary
Show Answer & NCERT Explanation
Correct Answer: (C) Primary → Secondary → Tertiary
Sewage treatment follows: Primary (physical — filtration, sedimentation) → Secondary (biological — aerobic microbes reduce BOD) → Tertiary (chemical disinfection).