15 extra multiple-choice questions for Microbes in Human Welfare (12th Standard Zoology, Samacheer Kalvi), beyond the ones printed in the textbook — each with the correct option highlighted and a clear, worked explanation. Free to read in English and Tamil.
Q1
Which of the following refers to the non-digestible food compounds, such as fibers, that selectively stimulate the growth and activity of beneficial microorganisms in the digestive tract?
- A. Probiotics
- B. Antibiotics
- C. PrebioticsCorrect
- D. Synbiotics
Explanation. Prebiotics are non-digestible food fibers that stimulate the growth of beneficial gut microbes. In contrast, probiotics are live beneficial microorganisms themselves.
Q2
The characteristic flavor of yogurt, produced by the fermentation of milk using Streptococcus thermophilus and Lactobacillus bulgaricus, is primarily due to which compound?
- A. AcetaldehydeCorrect
- B. Lactic acid
- C. Ethyl alcohol
- D. Acetic acid
Explanation. In yogurt production, Streptococcus thermophilus and Lactobacillus bulgaricus ferment lactose to produce lactic acid. The distinct and characteristic yogurt flavor is primarily due to the production of acetaldehyde.
Q3
Who discovered the antibiotic Streptomycin and was the first to introduce and use the term 'antibiotic' in the year 1943?
- A. Alexander Fleming
- B. Selman WaksmanCorrect
- C. Edward Jenner
- D. Louis Pasteur
Explanation. The microbiologist Selman Waksman discovered the antibiotic streptomycin in 1943. He was also the first scientist to coin and define the term antibiotic.
Q4
What is the name of the applied science that specifically deals with the biochemical processes of fermentation and its practical, industrial applications?
- A. ZymologyCorrect
- B. Mycology
- C. Biotechnology
- D. Bacteriology
Explanation. Zymology is the specialized applied science that studies the biochemical processes and practical uses of fermentation, especially in industrial production.
Q5
Which group of enzymes is commercially utilized to clarify bottled fruit juices by digesting structural plant cell wall components?
- A. Lipases and amylases
- B. Proteases, pectinases, and cellulasesCorrect
- C. Polymerases and ligases
- D. Dehydrogenases and isomerases
Explanation. During commercial juice processing, enzymes such as pectinases, proteases, and cellulases are utilized to digest plant cell wall elements and clarify the bottled juices.
Q6
A patient who has recently undergone myocardial infarction requires a 'clot buster' to remove blockages in their blood vessels. Which bioactive molecule is used for this purpose?
- A. Cyclosporin A
- B. Statins
- C. StreptokinaseCorrect
- D. Citric acid
Explanation. Genetically engineered Streptococci produce streptokinase, an enzyme that acts as a clot buster. It is clinically used to dissolve blood clots in patients who had a heart attack.
Q7
Under the National Policy on Biofuels approved by the Government of India in December 2009, which plant species was identified as the most suitable oilseed for biodiesel production?
- A. Jatropha curcasCorrect
- B. Pongamia pinnata
- C. Ricinus communis
- D. Brassica campestris
Explanation. The Indian National Policy on Biofuels of 2009 identified Jatropha curcas as the most appropriate oilseed plant for biodiesel production because of its high oil content.
Q8
Biogas is a mixture of gases produced by anaerobic microbial breakdown. What is the approximate percentage of methane, its primary combustible component, present in biogas?
- A. 50 percent
- B. 63 percentCorrect
- C. 75 percent
- D. 45 percent
Explanation. Biogas is generated through anaerobic microbial reactions. It is primarily composed of methane, which makes up about 63 percent of the gas mixture.
Q9
In a Microbial Fuel Cell (MFC), what is the primary role of the electrogenic bacteria residing at the anode chamber?
- A. To reduce carbon dioxide into methane gas
- B. To oxidize organic molecules and generate protons and electronsCorrect
- C. To synthesize complex carbohydrates from light energy
- D. To act as a proton exchange membrane between chambers
Explanation. In a microbial fuel cell, electrogenic bacteria at the anode oxidize organic fuel. This redox reaction releases protons and electrons, generating an electric current.
Q10
What was the first genetically engineered living organism to be patented in the world, developed by the scientist Ananda Mohan Chakrabarty?
- A. Saccharomyces cerevisiae
- B. Escherichia coli
- C. Pseudomonas putidaCorrect
- D. Ideonella sakaiensis
Explanation. Pseudomonas putida was the first living organism to be patented in 1980. It was genetically engineered by Ananda Mohan Chakrabarty to degrade hydrocarbons in oil spills.
Q11
Which of the following microorganisms is capable of degrading benzene under aerobic conditions, as well as a variety of halogenated organic compounds like trichloroethylene?
- A. Nitrosomonas europaeaCorrect
- B. Dechloromonas aromatica
- C. Dehalococcoides species
- D. Phanerochaete chrysosporium
Explanation. Nitrosomonas europaea is capable of aerobically degrading benzene. It can also break down various halogenated organic compounds, such as trichloroethylene and vinyl chloride.
Q12
The bacterium Ideonella sakaiensis is currently being investigated for recycling of PET plastics. Which enzymes does this bacterium use to break down PET?
- A. Pectinase and cellulase
- B. PETase and MHETaseCorrect
- C. Lipase and protease
- D. Amylase and zymase
Explanation. The plastic-recycling bacterium Ideonella sakaiensis produces two unique enzymes, PETase and MHETase. These enzymes break down PET plastic into its monomer components.
Q13
Which of the following anaerobic microbes has the specific ability to degrade benzene in the absence of oxygen, as well as oxidize toluene and xylene?
- A. Pseudomonas putida
- B. Dechloromonas aromaticaCorrect
- C. Pestalotiopsis microspora
- D. Aspergillus niger
Explanation. Dechloromonas aromatica is an anaerobic bacterium. It has the metabolic ability to degrade benzene and oxidize other aromatic pollutants like toluene and xylene in anaerobic conditions.
Q14
Which anaerobic fungus has shown strong potential for the bioremediation of toxic substances such as pesticides, polyaromatic hydrocarbons, trinitrotoluene, and cyanides?
- A. Pestalotiopsis microspora
- B. Phanerochaete chrysosporiumCorrect
- C. Trichoderma polysporum
- D. Saccharomyces cerevisiae
Explanation. Phanerochaete chrysosporium is an anaerobic fungus with strong bioremediation capabilities. It can degrade highly toxic pollutants like pesticides, polyaromatic hydrocarbons, dyes, TNT, and cyanides.
Q15
Which endophytic fungus has the unique capability of breaking down and digesting polyurethane, making it a promising candidate for bioremediating large quantities of plastics?
- A. Ideonella sakaiensis
- B. Pestalotiopsis microsporaCorrect
- C. Dehalococcoides species
- D. Rhizopus oryzae
Explanation. Pestalotiopsis microspora is an endophytic fungus. It is highly valued in bioremediation due to its unique ability to break down and digest polyurethane plastics.
