Prokaryotes – introduction MCQs With Answer offers B. Pharm students a focused, keyword-rich overview of bacterial and archaeal biology essential for pharmacy exams and practice. This concise introduction covers prokaryotic cell structure, peptidoglycan and cell wall differences, Gram staining, replication and transcription nuances, plasmids, antibiotic targets, metabolic diversity, horizontal gene transfer, quorum sensing, and clinical relevance. Each MCQ emphasizes pharmaceutically important concepts like resistance mechanisms, endotoxins, and sterilization to build applied understanding. Questions reinforce diagnostic and therapeutic implications, helping students connect microbiology fundamentals to drug action and safety.
Now let’s test your knowledge with 50 MCQs on this topic.
Q1. Which structure is unique to most bacteria but absent in archaea and eukaryotes?
- Peptidoglycan cell wall
- Phospholipid bilayer membrane
- 70S ribosomes
- Circular chromosome
Correct Answer: Peptidoglycan cell wall
Q2. During binary fission, what is the immediate event following DNA replication in bacteria?
- Formation of a septum
- Spore formation
- Endospore germination
- Chromosome linearization
Correct Answer: Formation of a septum
Q3. Which ribosomal subunit composition identifies prokaryotic ribosomes?
- 40S + 60S = 80S
- 30S + 50S = 70S
- 20S + 40S = 60S
- Large 80S ribosome only
Correct Answer: 30S + 50S = 70S
Q4. Gram-negative bacteria are characterized by which outer membrane component associated with endotoxin activity?
- Teichoic acid
- Lipopolysaccharide (LPS)
- Peptidoglycan teichoic layer
- Mycolic acid
Correct Answer: Lipopolysaccharide (LPS)
Q5. Which of the following best describes an operon common in bacterial gene regulation?
- Multiple promoters controlling one gene
- A cluster of genes transcribed from a single promoter
- Eukaryotic style intron-exon arrangement
- Linear plasmid replication unit
Correct Answer: A cluster of genes transcribed from a single promoter
Q6. Which horizontal gene transfer mechanism requires direct cell-to-cell contact mediated by a pilus?
- Transformation
- Transduction
- Conjugation
- Binary fission
Correct Answer: Conjugation
Q7. Bacterial endospores are primarily important because they:
- Promote rapid reproduction
- Enable survival in extreme conditions
- Facilitate horizontal gene transfer
- Increase antibiotic susceptibility
Correct Answer: Enable survival in extreme conditions
Q8. Which antibiotic class targets the 30S ribosomal subunit and inhibits protein synthesis?
- Beta-lactams
- Aminoglycosides
- Glycopeptides
- Fluoroquinolones
Correct Answer: Aminoglycosides
Q9. The Gram stain differentiates bacteria primarily based on differences in:
- Ribosomal RNA sequence
- Cell wall thickness and composition
- Metabolic pathway (aerobic vs anaerobic)
- Flagellar arrangement
Correct Answer: Cell wall thickness and composition
Q10. Which term describes bacteria that require oxygen for growth?
- Obligate anaerobes
- Facultative anaerobes
- Obligate aerobes
- Microaerophiles
Correct Answer: Obligate aerobes
Q11. Plasmids are important in pharmacy because they often carry genes for:
- Cellulose synthesis
- Antibiotic resistance
- Mitochondrial replication
- Ribosomal assembly
Correct Answer: Antibiotic resistance
Q12. Which structure aids bacterial attachment to surfaces and contributes to biofilm formation?
- Endospore
- Capsule or slime layer
- 70S ribosome
- Periplasmic space
Correct Answer: Capsule or slime layer
Q13. Which metabolic group of prokaryotes obtains energy from light but fixes CO2 like plants?
- Chemoheterotrophs
- Photoautotrophs (cyanobacteria)
- Chemoautotrophs
- Photoheterotrophs
Correct Answer: Photoautotrophs (cyanobacteria)
Q14. The Lac operon is an example of gene regulation responding to:
- Temperature only
- Presence or absence of lactose and glucose
- Oxygen concentration
- Antibiotic exposure
Correct Answer: Presence or absence of lactose and glucose
Q15. Which bacterial component is the primary target of beta-lactam antibiotics?
- DNA gyrase
- Peptidoglycan synthesis enzymes (transpeptidases)
- 30S ribosomal subunit
- Outer membrane LPS
Correct Answer: Peptidoglycan synthesis enzymes (transpeptidases)
Q16. Transformation as a gene transfer mechanism refers to:
- Transfer via bacteriophage
- Uptake of free naked DNA from the environment
- Transfer through conjugative pili
- Chromosomal segregation during cell division
Correct Answer: Uptake of free naked DNA from the environment
Q17. Which archaeal feature distinguishes archaea from bacteria?
- Presence of peptidoglycan
- Ether-linked membrane lipids
- 70S ribosomes
- Circular chromosome
Correct Answer: Ether-linked membrane lipids
Q18. Quorum sensing in bacteria primarily enables:
- DNA replication fidelity
- Population-density dependent gene regulation
- Spore formation only
- RNA splicing
Correct Answer: Population-density dependent gene regulation
Q19. Which stain is most useful to identify mycobacteria due to their high mycolic acid content?
- Gram stain
- Ziehl-Neelsen (acid-fast) stain
- Endospore stain
- Methylene blue simple stain
Correct Answer: Ziehl-Neelsen (acid-fast) stain
Q20. Which enzyme is targeted by fluoroquinolones in bacteria?
- RNA polymerase
- DNA gyrase (topoisomerase II)
- Transpeptidase
- Peptidyl transferase
Correct Answer: DNA gyrase (topoisomerase II)
Q21. Endotoxin released from Gram-negative bacteria during lysis is primarily responsible for:
- Disruption of peptidoglycan synthesis
- Septic shock and inflammatory responses
- Protein synthesis inhibition
- Flagellar motility
Correct Answer: Septic shock and inflammatory responses
Q22. Which prokaryotic DNA replication enzyme unwinds the double helix?
- DNA ligase
- Helicase
- DNA polymerase I
- Primase
Correct Answer: Helicase
Q23. Bacterial growth curve phase where cells adapt to new environment but do not yet divide rapidly is called:
- Logarithmic (exponential) phase
- Stationary phase
- Lag phase
- Death phase
Correct Answer: Lag phase
Q24. Which of the following bacteria lack a cell wall and are resistant to beta-lactam antibiotics?
- Staphylococcus aureus
- Mycoplasma species
- Escherichia coli
- Bacillus subtilis
Correct Answer: Mycoplasma species
Q25. Which method is commonly used to sterilize heat-stable medical instruments by denaturing proteins and nucleic acids?
- Autoclaving (moist heat, high pressure)
- UV radiation only
- Filtration through 0.45 µm
- Dry ice cooling
Correct Answer: Autoclaving (moist heat, high pressure)
Q26. Which bacterial structure is primarily involved in motility and chemotaxis?
- Pili
- Flagellum
- Capsule
- Periplasm
Correct Answer: Flagellum
Q27. Conjugative plasmids often carry genes for:
- Photosynthesis
- Antibiotic resistance and transfer functions
- Ribosomal RNA
- Endospore synthesis only
Correct Answer: Antibiotic resistance and transfer functions
Q28. Which enzyme synthesizes RNA primers required for DNA replication in bacteria?
- DNA polymerase III
- Primase
- Topoisomerase
- Ligase
Correct Answer: Primase
Q29. Transduction in bacteria involves gene transfer mediated by:
- Plasmids
- Bacteriophages
- Conjugative pili
- Free DNA uptake
Correct Answer: Bacteriophages
Q30. Which metabolic pathway is present in facultative anaerobes when oxygen is absent?
- Strict aerobic respiration only
- Fermentation or anaerobic respiration
- Photosynthesis
- Obligate anaerobic respiration only
Correct Answer: Fermentation or anaerobic respiration
Q31. Minimal inhibitory concentration (MIC) is best defined as:
- The highest antibiotic dose administered
- The lowest concentration of an antibiotic that prevents visible bacterial growth
- The concentration that kills 99.9% of organisms
- The minimal vaccine dose for immunity
Correct Answer: The lowest concentration of an antibiotic that prevents visible bacterial growth
Q32. Which bacterial structure contains enzymes and proteins involved in nutrient processing and transport in Gram-negative bacteria?
- Periplasmic space
- Cytoplasmic ribosome
- Capsular matrix
- Nucleoid
Correct Answer: Periplasmic space
Q33. Which statement about bacterial plasmid replication is correct?
- Plasmids always integrate into the chromosome
- Many plasmids replicate independently using their own origin of replication
- Plasmids are only linear molecules
- Plasmids encode mitochondrial proteins
Correct Answer: Many plasmids replicate independently using their own origin of replication
Q34. Which of the following is a common mechanism of bacterial resistance to aminoglycosides?
- Alteration of peptidoglycan cross-links
- Enzymatic modification of the antibiotic
- Increase in membrane permeability to the drug
- Overproduction of LPS
Correct Answer: Enzymatic modification of the antibiotic
Q35. Which genus of bacteria is known for forming characteristic endospores?
- Escherichia
- Bacillus
- Neisseria
- Mycoplasma
Correct Answer: Bacillus
Q36. Which molecule is the primary structural polymer of bacterial cell walls?
- Chitin
- Peptidoglycan (murein)
- Cellulose
- Hyaluronic acid
Correct Answer: Peptidoglycan (murein)
Q37. Which diagnostic culture medium contains bile salts and crystal violet to select for Gram-negative enteric bacteria?
- Mannitol salt agar
- MacConkey agar
- Blood agar
- Chocolate agar
Correct Answer: MacConkey agar
Q38. Bacterial transposons contribute to genetic variability by:
- Promoting vertical transmission only
- Moving DNA segments within and between genomes
- Preventing plasmid replication
- Inhibiting conjugation
Correct Answer: Moving DNA segments within and between genomes
Q39. Which bacterial secretion system is commonly associated with injection of effector proteins into host cells?
- Type III secretion system
- Type I secretion system
- Sec-dependent secretion only
- Autotransporter only
Correct Answer: Type III secretion system
Q40. Which acid-fast bacterium is a major cause of tuberculosis?
- Streptococcus pneumoniae
- Mycobacterium tuberculosis
- Escherichia coli
- Bacillus anthracis
Correct Answer: Mycobacterium tuberculosis
Q41. Which test differentiates bacteria based on their ability to ferment lactose producing acid?
- Oxidase test
- Lactose fermentation on MacConkey agar
- Coagulase test
- Gram stain
Correct Answer: Lactose fermentation on MacConkey agar
Q42. Which prokaryotic transcription enzyme is responsible for synthesizing mRNA?
- DNA polymerase III
- RNA polymerase
- Ribosome
- Reverse transcriptase
Correct Answer: RNA polymerase
Q43. Bacterial biofilms are clinically significant because they:
- Are easily eradicated by antibiotics
- Provide increased resistance to antibiotics and host defenses
- Always cause acute infections only
- Contain only planktonic cells
Correct Answer: Provide increased resistance to antibiotics and host defenses
Q44. Which component of peptidoglycan provides cross-linking between glycan chains?
- Polysaccharide capsule
- Peptide bridges (peptide side chains)
- Lipid A
- Teichoic acids only
Correct Answer: Peptide bridges (peptide side chains)
Q45. Which method is most appropriate to remove bacteria from a heat-sensitive liquid medication?
- Autoclaving
- Filtration through 0.22 µm membrane filter
- Boiling for 5 minutes
- Dry heat sterilization at 160°C
Correct Answer: Filtration through 0.22 µm membrane filter
Q46. Which bacterial protein is commonly used as a marker for phylogenetic classification due to conserved sequence?
- 16S rRNA
- DNA gyrase B protein only
- Peptidoglycan synthase
- Flagellin exclusively
Correct Answer: 16S rRNA
Q47. Which mechanism allows bacteria to alter outer membrane porins to reduce antibiotic uptake?
- Efflux pump activation only
- Mutation or regulation of porin proteins
- Endospore formation
- Increased ribosomal RNA synthesis
Correct Answer: Mutation or regulation of porin proteins
Q48. Which bacterial toxin type acts enzymatically inside host cells to modify host proteins (e.g., Diphtheria toxin)?
- Endotoxin
- Exotoxin with enzymatic activity (A-B toxin)
- Heat-stable enterotoxin only
- Lipid A derivative
Correct Answer: Exotoxin with enzymatic activity (A-B toxin)
Q49. Which statement correctly contrasts archaea and bacteria regarding antibiotic sensitivity?
- Archaea are generally sensitive to common antibiotics targeting peptidoglycan
- Bacteria lacking cell walls are highly sensitive to penicillin
- Many antibiotics targeting peptidoglycan synthesis are ineffective against archaea
- Both groups share identical antibiotic susceptibilities
Correct Answer: Many antibiotics targeting peptidoglycan synthesis are ineffective against archaea
Q50. In bacterial transcription termination, which mechanism involves formation of a GC-rich hairpin followed by uracil residues?
- Rho-dependent termination
- Rho-independent (intrinsic) termination
- Operon-based termination
- Splicing-dependent termination
Correct Answer: Rho-independent (intrinsic) termination
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