MIC 205 MODULES 1-4 EXAM QUESTIONS WITH VERIFIED SOLUTIONS
LATEST UPDATE 2026
What percentage of Earth's biodiversity is microbial? - Answers More than 50% of
Earth's biodiversity is microbial.
Why are microbes essential for life on Earth? - Answers They recycle nutrients,
decompose organic matter, fix nitrogen, produce oxygen, and support food webs.
What role do microbes play in the carbon cycle? - Answers They decompose dead
organisms and return carbon to the environment.
Which microbes are responsible for nitrogen fixation? - Answers Nitrogen-fixing
bacteria convert atmospheric nitrogen (N₂) into ammonia usable by plants.
Which microorganisms produce much of Earth's oxygen? - Answers Photosynthetic
cyanobacteria and marine phytoplankton.
Name three beneficial uses of microbes in medicine. - Answers Antibiotic
production, vaccine production, insulin production using recombinant DNA.
How do microbes benefit the digestive system? - Answers Normal microbiota aid
digestion, synthesize vitamins (especially vitamin K and some B vitamins), and
prevent pathogen colonization.
What is the normal microbiota? - Answers Microorganisms that normally live on or
in the body without causing disease.
How do microbes contribute to food production? - Answers Fermentation produces
yogurt, cheese, bread, beer, wine, vinegar, and pickled foods.
Give two environmental uses of microbes. - Answers Wastewater treatment and
bioremediation (oil spill cleanup).
What is bioremediation? - Answers The use of microorganisms to remove pollutants
from the environment.
Are all microbes harmful? - Answers No. Most microbes are beneficial or harmless;
only a small percentage are pathogenic.
What are the three domains of life? - Answers Bacteria, Archaea, and Eukarya.
Which domains are prokaryotic? - Answers Bacteria and Archaea.
Which domain contains organisms with membrane-bound organelles? - Answers
Eukarya.
What is the major defining feature of prokaryotes? - Answers They lack a membrane-
bound nucleus.
Where is DNA located in prokaryotes? - Answers In the nucleoid.
How many chromosomes do most bacteria possess? - Answers One circular
chromosome.
How many chromosomes do eukaryotes possess? - Answers Multiple linear
chromosomes.
Which cell type contains membrane-bound organelles? - Answers Eukaryotic cells.
Which ribosomes are found in prokaryotes? - Answers 70S ribosomes.
Which ribosomes are found in eukaryotic cytoplasm? - Answers 80S ribosomes.
Which cell type reproduces by binary fission? - Answers Prokaryotes.
Which cell type reproduces by mitosis? - Answers Eukaryotes.
Which cell type undergoes meiosis? - Answers Eukaryotes.
Which cell type is generally larger? - Answers Eukaryotes.
Which cells contain mitochondria? - Answers Eukaryotes.
Which cells contain chloroplasts? - Answers Plants and algae (eukaryotes).
Which cells have peptidoglycan? - Answers Bacteria only.
, Do archaea possess peptidoglycan? - Answers No.
Do viruses belong to either group? - Answers No, viruses are acellular.
What does the endosymbiotic theory explain? - Answers The origin of mitochondria
and chloroplasts.
Which organelles evolved through endosymbiosis? - Answers Mitochondria and
chloroplasts.
What type of bacteria gave rise to mitochondria? - Answers Aerobic bacteria.
What type of bacteria gave rise to chloroplasts? - Answers Cyanobacteria.
What evidence supports endosymbiotic theory? - Answers Circular DNA, 70S
ribosomes, binary fission, double membranes, bacterial size.
Why do mitochondria have their own DNA? - Answers They evolved from free-
living bacteria.
Why do chloroplasts contain 70S ribosomes? - Answers They originated from
bacteria.
Why is endosymbiotic theory important? - Answers It explains the evolution of
complex eukaryotic cells.
What is the function of the bacterial cell wall? - Answers Maintains shape and
prevents osmotic lysis.
What is peptidoglycan? - Answers A polymer unique to bacterial cell walls.
Which bacteria have thick peptidoglycan? - Answers Gram-positive bacteria.
Which bacteria have thin peptidoglycan? - Answers Gram-negative bacteria.
Which bacteria possess an outer membrane? - Answers Gram-negative bacteria.
Which stain colors Gram-positive bacteria purple? - Answers Crystal violet.
Which stain colors Gram-negative bacteria pink? - Answers Safranin.
Why do Gram-positive bacteria remain purple? - Answers Thick peptidoglycan
retains the crystal violet-iodine complex.
Why do Gram-negative bacteria become pink? - Answers Alcohol removes crystal
violet because of thin peptidoglycan.
What is the function of the plasma membrane? - Answers Selective transport and
ATP production.
What is the nucleoid? - Answers Region containing bacterial chromosome.
What are plasmids? - Answers Small circular DNA molecules carrying extra genes.
Why are plasmids medically important? - Answers They often carry antibiotic
resistance genes.
Function of ribosomes? - Answers Protein synthesis.
Function of capsule? - Answers Prevents phagocytosis and aids adhesion.
Function of fimbriae? - Answers Attachment to surfaces.
Function of pili? - Answers DNA transfer during conjugation.
Function of flagella? - Answers Motility.
What are endospores? - Answers Dormant, highly resistant survival structures.
Which genera commonly form endospores? - Answers Bacillus and Clostridium.
Are endospores reproductive structures? - Answers No.
What is selective toxicity? - Answers Drugs harm microbes while causing minimal
damage to host cells.
Why is peptidoglycan an excellent antibiotic target? - Answers Human cells lack
peptidoglycan.
Why are bacterial ribosomes antibiotic targets? - Answers Bacterial 70S ribosomes
differ from human 80S ribosomes.
Which antibiotics inhibit peptidoglycan synthesis? - Answers Penicillins and
cephalosporins.
LATEST UPDATE 2026
What percentage of Earth's biodiversity is microbial? - Answers More than 50% of
Earth's biodiversity is microbial.
Why are microbes essential for life on Earth? - Answers They recycle nutrients,
decompose organic matter, fix nitrogen, produce oxygen, and support food webs.
What role do microbes play in the carbon cycle? - Answers They decompose dead
organisms and return carbon to the environment.
Which microbes are responsible for nitrogen fixation? - Answers Nitrogen-fixing
bacteria convert atmospheric nitrogen (N₂) into ammonia usable by plants.
Which microorganisms produce much of Earth's oxygen? - Answers Photosynthetic
cyanobacteria and marine phytoplankton.
Name three beneficial uses of microbes in medicine. - Answers Antibiotic
production, vaccine production, insulin production using recombinant DNA.
How do microbes benefit the digestive system? - Answers Normal microbiota aid
digestion, synthesize vitamins (especially vitamin K and some B vitamins), and
prevent pathogen colonization.
What is the normal microbiota? - Answers Microorganisms that normally live on or
in the body without causing disease.
How do microbes contribute to food production? - Answers Fermentation produces
yogurt, cheese, bread, beer, wine, vinegar, and pickled foods.
Give two environmental uses of microbes. - Answers Wastewater treatment and
bioremediation (oil spill cleanup).
What is bioremediation? - Answers The use of microorganisms to remove pollutants
from the environment.
Are all microbes harmful? - Answers No. Most microbes are beneficial or harmless;
only a small percentage are pathogenic.
What are the three domains of life? - Answers Bacteria, Archaea, and Eukarya.
Which domains are prokaryotic? - Answers Bacteria and Archaea.
Which domain contains organisms with membrane-bound organelles? - Answers
Eukarya.
What is the major defining feature of prokaryotes? - Answers They lack a membrane-
bound nucleus.
Where is DNA located in prokaryotes? - Answers In the nucleoid.
How many chromosomes do most bacteria possess? - Answers One circular
chromosome.
How many chromosomes do eukaryotes possess? - Answers Multiple linear
chromosomes.
Which cell type contains membrane-bound organelles? - Answers Eukaryotic cells.
Which ribosomes are found in prokaryotes? - Answers 70S ribosomes.
Which ribosomes are found in eukaryotic cytoplasm? - Answers 80S ribosomes.
Which cell type reproduces by binary fission? - Answers Prokaryotes.
Which cell type reproduces by mitosis? - Answers Eukaryotes.
Which cell type undergoes meiosis? - Answers Eukaryotes.
Which cell type is generally larger? - Answers Eukaryotes.
Which cells contain mitochondria? - Answers Eukaryotes.
Which cells contain chloroplasts? - Answers Plants and algae (eukaryotes).
Which cells have peptidoglycan? - Answers Bacteria only.
, Do archaea possess peptidoglycan? - Answers No.
Do viruses belong to either group? - Answers No, viruses are acellular.
What does the endosymbiotic theory explain? - Answers The origin of mitochondria
and chloroplasts.
Which organelles evolved through endosymbiosis? - Answers Mitochondria and
chloroplasts.
What type of bacteria gave rise to mitochondria? - Answers Aerobic bacteria.
What type of bacteria gave rise to chloroplasts? - Answers Cyanobacteria.
What evidence supports endosymbiotic theory? - Answers Circular DNA, 70S
ribosomes, binary fission, double membranes, bacterial size.
Why do mitochondria have their own DNA? - Answers They evolved from free-
living bacteria.
Why do chloroplasts contain 70S ribosomes? - Answers They originated from
bacteria.
Why is endosymbiotic theory important? - Answers It explains the evolution of
complex eukaryotic cells.
What is the function of the bacterial cell wall? - Answers Maintains shape and
prevents osmotic lysis.
What is peptidoglycan? - Answers A polymer unique to bacterial cell walls.
Which bacteria have thick peptidoglycan? - Answers Gram-positive bacteria.
Which bacteria have thin peptidoglycan? - Answers Gram-negative bacteria.
Which bacteria possess an outer membrane? - Answers Gram-negative bacteria.
Which stain colors Gram-positive bacteria purple? - Answers Crystal violet.
Which stain colors Gram-negative bacteria pink? - Answers Safranin.
Why do Gram-positive bacteria remain purple? - Answers Thick peptidoglycan
retains the crystal violet-iodine complex.
Why do Gram-negative bacteria become pink? - Answers Alcohol removes crystal
violet because of thin peptidoglycan.
What is the function of the plasma membrane? - Answers Selective transport and
ATP production.
What is the nucleoid? - Answers Region containing bacterial chromosome.
What are plasmids? - Answers Small circular DNA molecules carrying extra genes.
Why are plasmids medically important? - Answers They often carry antibiotic
resistance genes.
Function of ribosomes? - Answers Protein synthesis.
Function of capsule? - Answers Prevents phagocytosis and aids adhesion.
Function of fimbriae? - Answers Attachment to surfaces.
Function of pili? - Answers DNA transfer during conjugation.
Function of flagella? - Answers Motility.
What are endospores? - Answers Dormant, highly resistant survival structures.
Which genera commonly form endospores? - Answers Bacillus and Clostridium.
Are endospores reproductive structures? - Answers No.
What is selective toxicity? - Answers Drugs harm microbes while causing minimal
damage to host cells.
Why is peptidoglycan an excellent antibiotic target? - Answers Human cells lack
peptidoglycan.
Why are bacterial ribosomes antibiotic targets? - Answers Bacterial 70S ribosomes
differ from human 80S ribosomes.
Which antibiotics inhibit peptidoglycan synthesis? - Answers Penicillins and
cephalosporins.
