biology : class12 Methanotrophic Bacteria : Definition, Sources, Nutritional Importance : Single Cell Protein MCQ Questions and Answers
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Methanotrophic Bacteria
MCQ questions and answers.
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MCQ Questions
1. Why are methanotrophic bacteria considered suitable organisms for producing single-cell protein from methane-rich gas?
A.
They oxidize methane as a carbon and energy source while generating biomass rich in cellular protein
B.
They convert methane directly into atmospheric nitrogen and store it as protein
C.
They use methane only as a nitrogen source and obtain carbon from atmospheric carbon dioxide
D.
They ferment methane anaerobically into starch, which is then incorporated into their cells
Correct Answer:
They oxidize methane as a carbon and energy source while generating biomass rich in cellular protein
Explanation:
Methanotrophic bacteria use methane as their principal carbon and energy source. Their growth produces microbial biomass containing substantial protein, making that biomass useful as single-cell protein.
2. Which metabolic conversion is the essential first step in the aerobic utilization of methane by methanotrophic bacteria?
A.
Oxidation of methane to methanol
B.
Reduction of methane to methylamine
C.
Conversion of methane directly into acetate by fermentation
D.
Oxidation of methane to carbon monoxide without an alcohol intermediate
Correct Answer:
Oxidation of methane to methanol
Explanation:
Aerobic methanotrophs begin methane utilization by oxidizing methane to methanol through methane monooxygenase. Methanol is then further metabolized to supply carbon and energy for cell growth.
3. A bioreactor intended to cultivate methanotrophic bacteria for single-cell protein would most directly require which combination of inputs?
A.
Methane, oxygen, mineral nutrients, water, and a suitable source of nitrogen
B.
Methane, nitrate-free water, cellulose, and hydrogen sulfide under strictly anaerobic conditions
C.
Glucose, oxygen, methane, and an absence of inorganic nitrogen
D.
Methane, starch, molecular nitrogen only, and complete exclusion of oxygen
Correct Answer:
Methane, oxygen, mineral nutrients, water, and a suitable source of nitrogen
Explanation:
Aerobic methanotrophic growth requires methane as the carbon-energy substrate, oxygen for methane oxidation, water, mineral salts, and nitrogen for synthesizing cellular proteins and nucleic acids.
4. Which statement best distinguishes methane-based single-cell protein production by methanotrophs from conventional plant protein production?
A.
Methanotrophs can generate protein-rich biomass rapidly using methane as a substrate without requiring agricultural land for crop cultivation
B.
Methanotrophs synthesize protein only after methane has first been converted into soil humus by plants
C.
Methanotrophic biomass contains no nucleic acids, unlike plant cells
D.
Methanotrophs require sunlight and chlorophyll to convert methane into amino acids
Correct Answer:
Methanotrophs can generate protein-rich biomass rapidly using methane as a substrate without requiring agricultural land for crop cultivation
Explanation:
Methanotrophic bacteria grow rapidly on methane and can be cultivated in controlled systems, providing microbial protein without the land area and long crop-growth period required for plants.
5. Why must oxygen availability be carefully controlled in an aerobic methanotroph-based single-cell protein reactor?
A.
Oxygen is required for methane oxidation, but an unsuitable methane-to-oxygen balance can reduce growth and create safety hazards
B.
Oxygen is used only to fix atmospheric nitrogen, and excess oxygen always increases methane utilization
C.
Methanotrophs use oxygen only for photosynthesis, so oxygen is unnecessary when methane concentration is high
D.
Oxygen prevents methanotrophs from producing biomass and must therefore be completely removed
Correct Answer:
Oxygen is required for methane oxidation, but an unsuitable methane-to-oxygen balance can reduce growth and create safety hazards
Explanation:
Aerobic methanotrophs need oxygen for methane monooxygenase-mediated oxidation. Because methane-oxygen mixtures can also be hazardous, reactor gas composition must be controlled for both biological performance and operational safety.
6. Which feature of methanotrophic bacterial biomass is most directly responsible for its nutritional importance as single-cell protein?
A.
A high proportion of cellular dry mass may consist of protein containing several essential amino acids
B.
The biomass consists exclusively of crystalline amino acids and contains no nucleic acids
C.
The cells store methane unchanged, making the biomass an unusually concentrated hydrocarbon food
D.
The cells contain chlorophyll, which supplies dietary energy after ingestion
Correct Answer:
A high proportion of cellular dry mass may consist of protein containing several essential amino acids
Explanation:
Methanotrophs produce protein-rich microbial cells. This high protein content, including nutritionally valuable amino acids, is the primary reason their biomass can serve as single-cell protein.
7. A gas stream contains methane but no usable nitrogen source. What is the most likely immediate limitation on methanotrophic biomass production?
A.
Protein and nucleic-acid synthesis will be restricted despite the availability of methane
B.
Methane will be unable to dissolve in water because nitrogen is required for methane oxidation
C.
Methane monooxygenase will convert methane into cellulose instead of methanol
D.
The bacteria will obtain unlimited nitrogen by converting methane carbon into atmospheric nitrogen
Correct Answer:
Protein and nucleic-acid synthesis will be restricted despite the availability of methane
Explanation:
Methane supplies carbon and energy, but nitrogen is also essential for amino acids, proteins, nucleic acids, and other cellular components. Nitrogen deficiency therefore limits methanotrophic biomass formation.
8. Which observation would most strongly indicate that a culture is actively growing methanotrophically rather than merely surviving in a methane-containing vessel?
A.
A decrease in methane concentration accompanied by increased cell mass and oxygen consumption
B.
A decrease in methane concentration with no increase in biomass and no oxygen use
C.
An increase in methane concentration accompanied by disappearance of mineral nutrients
D.
Stable methane concentration with rapid production of chlorophyll under darkness
Correct Answer:
A decrease in methane concentration accompanied by increased cell mass and oxygen consumption
Explanation:
Active aerobic methanotrophic growth consumes methane and oxygen while converting methane-derived carbon into new cellular material. The combined changes provide stronger evidence than methane disappearance alone.
9. Why is methane considered an attractive feedstock for methanotrophic single-cell protein production when it is available as a by-product of waste treatment or natural-gas operations?
A.
It is an energy-rich reduced one-carbon compound that can be converted into microbial biomass by specialized bacteria
B.
It is a nitrogen-rich compound that directly supplies all amino acids without microbial metabolism
C.
It is a polysaccharide that methanotrophs hydrolyze into glucose before protein synthesis
D.
It is biologically inert, so it accumulates inside cells without being oxidized
Correct Answer:
It is an energy-rich reduced one-carbon compound that can be converted into microbial biomass by specialized bacteria
Explanation:
Methane contains substantial chemical energy and provides a one-carbon substrate for methanotrophs. Its conversion into cell material allows otherwise underused methane-rich gases to support protein production.
10. Which sequence most accurately represents the flow of methane-derived carbon during aerobic growth of a methanotrophic bacterium?
A.
Methane to methanol to formaldehyde or related assimilable intermediates, followed by incorporation into cellular material
B.
Methane to starch to cellulose, followed by oxidation into cellular protein
C.
Methane to molecular nitrogen to ammonia, followed by conversion into amino-acid carbon skeletons
D.
Methane to oxygen to carbon dioxide, with no intermediate carbon compounds involved in biomass formation
Correct Answer:
Methane to methanol to formaldehyde or related assimilable intermediates, followed by incorporation into cellular material
Explanation:
Aerobic methanotrophic metabolism starts with methane oxidation to methanol and proceeds through C1 intermediates such as formaldehyde. These intermediates can be assimilated into biomass, including protein.
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