Antibiotics MCQs For NEET Biology With Explanation, Practice Now

What is Antibiotics? 

Antibiotics are medicines made from microbes that help fight bacterial infections. They either kill the bacteria or stop them from growing further. Antibiotics do not work against viruses. The first antibiotic discovered was penicillin, found by Alexander Fleming in 1928.

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Antibiotics MCQs with Explanations

Here are some important Antibiotics-related MCQs for NEET:

Q1. The flocs in sewage treatment are:

1. masses of anaerobic bacteria

2. masses of aerobic fungi only

3. masses of anaerobic bacteria and fungi

4. masses of aerobic bacteria associated with fungal filament

Answer: (D)

Explanation: Flocs are loose masses of aerobic bacteria that grow on organic matter in the aeration tank during secondary treatment of sewage. These bacteria are often attached to fungal filaments, forming mesh-like structures that help in settling the organic matter.

Q2. Brewer's yeast is: 

1. Saccharomyces cerevisiae

2. Penicillium notatum

3. Trichoderma polysporum

4. Monascus purpureus

Answer: (A)

Explanation: Saccharomyces cerevisiae, also known as brewer’s or baker’s yeast, is used for fermentation in alcohol production and bread-making.

Q3. Read the following statements:

I. Anti is a Greek word that means against and bio means life in antibiotics.

II. The gases from biogas can be used as source of energy as it is inflammable.

III. The activated sludge is formed during the secondary treatment of sewage.

IV. Lactic acid bacteria improves the nutritional quality of curd by increasing vitamin B₆.

 Choose the correct option:

1. I, II and III only

2. Only III

3. I and IV only

4. II and IV only

Answer: (A)

Explanation: Statements I, II, and III are true. Statement IV is incorrect because lactic acid bacteria improve curd by increasing vitamin B₁₂, not B₆.

Q4. The greater the BOD of waste water, ______ is its polluting potential.

1. More

2. Less

3. Same

4. zero

Answer: (A)

Explanation: BOD (Biochemical Oxygen Demand) indicates the amount of organic matter in water. A higher BOD means more pollution because more oxygen is needed by microbes to decompose waste.

Q5. Treatment of wastewater is done by the: 

1. photoautotrophic microbes

2. chemoautotrophic microbes

3. heterotrophic microbes

4. heterotrophic microbes inoculated from outside

Answer: (C)

Explanation: Naturally present heterotrophic microbes in sewage play the key role in decomposing organic matter during wastewater treatment.

Q6. The diagram of a typical biogas plant has labels A, B, and C. What do they represent?

1. A-Sludge, B-Dung + Water, C-Gas holder

2. A-Dung + Water, B-Sludge, C-CH₄ + CO₂

3. A-Sludge, B-Gas holder, C-Dung + Water

4. A-CH₄ + CO₂, B-Dung + Water, C-Sludge

Answer: (C)

Explanation: In a biogas plant, sludge settles at the bottom (A), gas collects in the dome (B), and the dung-water mix enters from the inlet (C)

Q7. Production on an industrial scale requires growing microbes in large vessels called:

1. fermentors

2. chemicals

3. enzymes

4. organic farming

Answer: (A)

Explanation: Microbes are grown in large steel tanks called fermentors for large-scale production of beverages, antibiotics, and enzymes.

Q8. Statement-I: A major component of waste water is human excreta.

Statement-II: The municipal wastewater is also called sewage. 

1. I correct, II incorrect

2. I incorrect, II correct

3. Both correct

4. Both incorrect

Answer: (C)

Explanation: Both statements are true. Human excreta is a major component of sewage, which is the municipal wastewater.

Q9. Statement-I: Penicillin was the first antibiotic to be discovered.

Statement-II: Alexander Fleming observed a mould growing on a plate of Staphylococci cultures.

1. I correct, II incorrect

2. I incorrect, II correct

3. Both correct

4. Both incorrect

Answer: (C)

Explanation: Both are correct. Alexander Fleming discovered penicillin from Penicillium notatum in 1928.

Q10. All solids in the primary treatment that settle from the:

1. primary sludge

2. effluent

3. flocs

4. activated sludge

Answer: (A)

Explanation: In primary treatment, solids settle at the bottom and form primary sludge, while the liquid moves on for further treatment.

Q11. Which of the following is not a nitrogen-fixing organism?

1. Anabaena

2. Nostoc

3. Azotobacter

4. Aspergillus

Answer: (D)

Explanation: Aspergillus is a fungus and does not fix nitrogen, unlike the other options, which are known nitrogen-fixers.

Q12. The dough used for making idli and dosa is fermented by:

1. Bacteria

2. Aspergillus

3. Oscillatoria

4. Nostoc

Answer: (A)

Explanation: The fermentation of dosa/idli batter is carried out by lactic acid bacteria that produce acids, improving texture and taste.

Q13. The antibiotic penicillin is obtained from:

1. Penicillium notatum

2. Staphylococci

3. Trichoderma

4. Monascus

Answer: (A)

Explanation: Penicillin, the first widely used antibiotic, is produced by the fungus Penicillium notatum.

Q14. Assertion (A): Bottled fruit juices made at home are clearer than those from the market.

Reason (R): Bottled juices are clarified by the use of pectinases and proteases.

1. A true, R false

2. A false, R true

3. Both true; R explains A

4. Both are true, but R does not explain A

Answer: (B)

Explanation: Market juices are clearer than homemade ones because they are treated with enzymes like pectinase and protease.

Q15. Assertion (A): Baculoviruses are pathogens that attack fungi and other bacteria.

Reason (R): Baculoviruses are species-specific, narrow-spectrum insecticidal agents. 

1. A true, R false

2. A false, R true

3. Both true; R explains A

4. Both are true, but R does not explain A

Answer: (B)

Explanation: Baculoviruses attack insects (not fungi or bacteria). The reason is correct, but the assertion is false.

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