Try each question on your own first. Use the Show Answer button only after you have selected your option, then read the explanation and revise the related concept from your chapter notes.
1. Lactobacillus, a well-known beneficial bacterium, is commonly used in the production of:
A. Curd from milk
B. Bread exclusively
C. Antibiotics
D. Biogas
Answer: A. Curd from milk
Explanation: Lactobacillus (commonly called lactic acid bacteria) ferments milk sugars to produce lactic acid, converting milk into curd.
2. The yeast Saccharomyces cerevisiae is widely used industrially in the production of:
A. Wine, beer and bread
B. Curd
C. Antibiotics
D. Cheese exclusively
Answer: A. Wine, beer and bread
Explanation: This yeast species ferments sugars to produce alcohol and carbon dioxide, key processes in both brewing/winemaking and baking.
3. Penicillin, one of the earliest antibiotics discovered, is naturally obtained from the:
A. Fungus Penicillium notatum
B. A species of bacterium
C. A type of virus
D. A type of protozoan
Answer: A. Fungus Penicillium notatum
Explanation: Alexander Fleming discovered that the mould Penicillium notatum produced a substance capable of killing certain bacteria.
4. Biogas, a clean and renewable fuel, is produced through the action of:
A. Methanogenic bacteria
B. Fungi
C. Algae exclusively
D. Viruses
Answer: A. Methanogenic bacteria
Explanation: Methanogens are anaerobic bacteria that break down organic waste to release methane-rich biogas as a by-product.
5. Biofertilizers help enrich soil fertility mainly through the activity of organisms such as:
A. Nitrogen-fixing bacteria like Rhizobium
B. Disease-causing pathogenic bacteria
C. Viruses
D. Purely chemical compounds
Answer: A. Nitrogen-fixing bacteria like Rhizobium
Explanation: Rhizobium, living symbiotically in the root nodules of legumes, converts atmospheric nitrogen into a usable form for plants.
6. The secondary (biological) stage of sewage treatment relies mainly on the activity of:
A. Microorganisms that break down organic matter present in the sewage
B. Chemical filtration alone
C. UV radiation alone
D. Simple physical settling alone
Answer: A. Microorganisms that break down organic matter present in the sewage
Explanation: In the secondary treatment stage, aerobic microbes consume and break down the organic pollutants in sewage, significantly reducing the BOD.
7. The characteristic large holes seen in Swiss cheese are produced due to gas released by the bacterium:
A. Propionibacterium sharmanii
B. Lactobacillus
C. Saccharomyces
D. Rhizobium
Answer: A. Propionibacterium sharmanii
Explanation: During fermentation, this bacterium releases carbon dioxide gas, which creates the characteristic large holes in Swiss cheese.
8. Streptokinase, used clinically as a 'clot buster' in heart attack patients, is produced with the help of:
A. The bacterium Streptococcus, modified through genetic engineering
B. A type of virus
C. A type of fungus exclusively
D. A species of algae
Answer: A. The bacterium Streptococcus, modified through genetic engineering
Explanation: Streptokinase, originally derived from Streptococcus bacteria, is now produced through genetically modified bacteria for medical use.
9. Biological control of agricultural pests, as an eco-friendly alternative to chemical pesticides, commonly uses organisms such as:
A. Bacillus thuringiensis
B. Yeast exclusively
C. Lactobacillus exclusively
D. Penicillium exclusively
Answer: A. Bacillus thuringiensis
Explanation: Bacillus thuringiensis produces a protein toxic to specific insect larvae, making it a widely used biological pesticide.
10. In sewage treatment, the parameter known as Biochemical Oxygen Demand (BOD) indicates the:
A. Amount of organic matter present, based on the oxygen consumed by microbes during its breakdown
B. Total physical volume of sewage
C. Amount of chemicals artificially added
D. Level of pathogens present only
Answer: A. Amount of organic matter present, based on the oxygen consumed by microbes during its breakdown
Explanation: A higher BOD value reflects greater organic pollution, since more oxygen is consumed by microbes decomposing the waste.
11. Single-cell protein (SCP), an application of microbes such as the alga Spirulina, refers to their use as a:
A. Protein-rich food or feed supplement
B. Source of fuel exclusively
C. Source of antibiotics exclusively
D. Type of fertilizer exclusively
Answer: A. Protein-rich food or feed supplement
Explanation: Microorganisms like Spirulina can be cultured on a large scale to provide an inexpensive, protein-rich dietary supplement.
12. The industrial-scale production of citric acid commonly uses the fungus:
A. Aspergillus niger
B. Saccharomyces cerevisiae
C. Lactobacillus
D. Rhizobium
Answer: A. Aspergillus niger
Explanation: Aspergillus niger is widely employed in fermentation processes to produce citric acid on a commercial scale.
