Bacterial Structure & Function
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All Questions for: Bacterial Structure & Function
Question 1: Bacteria are classified as:
- A Prokaryotes
- B Eukaryotes
- C Viruses
- D Fungi
Explanation: Bacteria are prokaryotes — they lack a membrane-bound nucleus and organelles.
Question 2: The bacterial cell wall is primarily composed of:
- A Peptidoglycan
- B Cellulose
- C Chitin
- D Lignin
Explanation: Bacterial cell walls contain peptidoglycan (murein), unique to bacteria.
Question 3: Gram-positive bacteria have cell walls with:
- A Thick peptidoglycan layer
- B Thin peptidoglycan with outer membrane
- C No peptidoglycan
- D Cellulose walls
Explanation: Gram-positive bacteria have a thick peptidoglycan layer that retains crystal violet stain.
Question 4: Gram-negative bacteria have cell walls with:
- A Thin peptidoglycan and outer membrane
- B Thick peptidoglycan only
- C No outer membrane
- D Cellulose walls
Explanation: Gram-negative bacteria have a thin peptidoglycan layer and an outer lipopolysaccharide membrane.
Question 5: The Gram stain distinguishes bacteria based on:
- A Cell wall structure
- B Presence of nucleus
- C Flagella type
- D Colony shape
Explanation: Gram staining differentiates bacteria by their cell wall structure (thickness of peptidoglycan).
Question 6: Endotoxin is a component of:
- A Gram-negative bacteria
- B Gram-positive bacteria
- C Viruses
- D Fungi
Explanation: Endotoxin (LPS) is found in the outer membrane of Gram-negative bacteria.
Question 7: Exotoxins are:
- A Proteins secreted by bacteria
- B Lipopolysaccharides
- C Cell wall components
- D DNA fragments
Explanation: Exotoxins are proteins secreted by bacteria, often highly potent toxins.
Question 8: Flagella are used by bacteria for:
- A Movement
- B Reproduction
- C Photosynthesis
- D Feeding
Explanation: Flagella are used for motility (movement).
Question 9: Pili (fimbriae) are used for:
- A Attachment and conjugation
- B Movement
- C Reproduction
- D Photosynthesis
Explanation: Pili mediate attachment to surfaces and conjugation (DNA transfer).
Question 10: Bacterial DNA is:
- A A single circular chromosome
- B Multiple linear chromosomes
- C Always RNA
- D No genetic material
Explanation: Bacteria typically have a single circular chromosome and may also contain plasmids.
Question 11: Plasmids are:
- A Small circular extrachromosomal DNA
- B Part of the chromosome
- C Membrane proteins
- D Ribosomes
Explanation: Plasmids are small, circular DNA molecules that replicate independently of the chromosome.
Question 12: Bacterial ribosomes are:
- A 70S
- B 80S
- C 60S
- D 40S
Explanation: Bacterial ribosomes are 70S (30S + 50S subunits), differing from eukaryotic 80S ribosomes.
Question 13: Endospores are formed by which genera?
- A Bacillus and Clostridium
- B E. coli and Salmonella
- C Staphylococcus and Streptococcus
- D Mycobacterium and Corynebacterium
Explanation: Endospores are formed by Bacillus and Clostridium species for survival in harsh conditions.
Question 14: Endospores are primarily for:
- A Survival in harsh conditions
- B Reproduction
- C Movement
- D Photosynthesis
Explanation: Endospores are dormant survival forms, resistant to heat, radiation, and chemicals.
Question 15: Capsule in bacteria functions primarily to:
- A Protect against phagocytosis
- B Provide motility
- C Produce ATP
- D Synthesize proteins
Explanation: Capsules protect bacteria from phagocytosis and aid adherence.
Question 16: Mesosomes are:
- A Infoldings of the plasma membrane
- B Small ribosomes
- C Plasmids
- D Flagellar proteins
Explanation: Mesosomes are infoldings of the plasma membrane in bacteria (functions debated).
Question 17: Mycobacterium species are:
- A Acid-fast due to mycolic acid
- B Gram-positive only
- C Without cell walls
- D Always pathogenic
Explanation: Mycobacteria have waxy cell walls with mycolic acid, making them acid-fast.
Question 18: Which is NOT a bacterial shape?
- A Amoeboid
- B Cocci
- C Bacilli
- D Spirilla
Explanation: Bacterial shapes include cocci, bacilli, spirilla; 'amoeboid' is not a bacterial shape.
Question 19: Cocci are:
- A Spherical
- B Rod-shaped
- C Spiral
- D Comma-shaped
Explanation: Cocci are spherical bacteria.
Question 20: Bacilli are:
- A Rod-shaped
- B Spherical
- C Spiral
- D Comma-shaped
Explanation: Bacilli are rod-shaped bacteria.
Question 21: Spirilla are:
- A Spiral-shaped
- B Rod-shaped
- C Spherical
- D Comma-shaped
Explanation: Spirilla are spiral-shaped bacteria.
Question 22: Vibrio bacteria are:
- A Comma-shaped
- B Spherical
- C Rod-shaped
- D Spiral-shaped
Explanation: Vibrio are comma-shaped bacteria, e.g., Vibrio cholerae.
Question 23: Conjugation is:
- A DNA transfer via direct contact
- B DNA transfer via bacteriophage
- C Uptake of free DNA
- D Cell division
Explanation: Conjugation is bacterial DNA transfer through direct cell-to-cell contact via a sex pilus.
Question 24: Transformation in bacteria refers to:
- A Uptake of free DNA
- B DNA transfer via contact
- C DNA transfer via virus
- D Cell division
Explanation: Transformation is the uptake of free DNA from the environment by competent cells.
Question 25: Transduction in bacteria refers to:
- A DNA transfer via bacteriophage
- B Uptake of free DNA
- C Direct cell contact
- D Cell division
Explanation: Transduction is DNA transfer between bacteria via a bacteriophage (virus).