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TestMaster MCQs

Bacterial Structure & Function Questions

Home Science Bacterial Structure & Function
Q. Bacteria are classified as:
Viruses
Fungi
Eukaryotes
Prokaryotes

Explanation:

Bacteria are prokaryotes — they lack a membrane-bound nucleus and organelles.

Q. The bacterial cell wall is primarily composed of:
Cellulose
Peptidoglycan
Chitin
Lignin

Explanation:

Bacterial cell walls contain peptidoglycan (murein), unique to bacteria.

Q. Gram-positive bacteria have cell walls with:
Thick peptidoglycan layer
Thin peptidoglycan with outer membrane
No peptidoglycan
Cellulose walls

Explanation:

Gram-positive bacteria have a thick peptidoglycan layer that retains crystal violet stain.

Q. Gram-negative bacteria have cell walls with:
Thick peptidoglycan only
Thin peptidoglycan and outer membrane
Cellulose walls
No outer membrane

Explanation:

Gram-negative bacteria have a thin peptidoglycan layer and an outer lipopolysaccharide membrane.

Q. The Gram stain distinguishes bacteria based on:
Colony shape
Cell wall structure
Flagella type
Presence of nucleus

Explanation:

Gram staining differentiates bacteria by their cell wall structure (thickness of peptidoglycan).

Q. Endotoxin is a component of:
Fungi
Gram-negative bacteria
Viruses
Gram-positive bacteria

Explanation:

Endotoxin (LPS) is found in the outer membrane of Gram-negative bacteria.

Q. Exotoxins are:
Cell wall components
Proteins secreted by bacteria
DNA fragments
Lipopolysaccharides

Explanation:

Exotoxins are proteins secreted by bacteria, often highly potent toxins.

Q. Flagella are used by bacteria for:
Feeding
Movement
Photosynthesis
Reproduction

Explanation:

Flagella are used for motility (movement).

Q. Pili (fimbriae) are used for:
Movement
Reproduction
Attachment and conjugation
Photosynthesis

Explanation:

Pili mediate attachment to surfaces and conjugation (DNA transfer).

Q. Bacterial DNA is:
A single circular chromosome
Multiple linear chromosomes
Always RNA
No genetic material

Explanation:

Bacteria typically have a single circular chromosome and may also contain plasmids.

Q. Plasmids are:
Small circular extrachromosomal DNA
Membrane proteins
Ribosomes
Part of the chromosome

Explanation:

Plasmids are small, circular DNA molecules that replicate independently of the chromosome.

Q. Bacterial ribosomes are:
40S
80S
60S
70S

Explanation:

Bacterial ribosomes are 70S (30S + 50S subunits), differing from eukaryotic 80S ribosomes.

Q. Endospores are formed by which genera?
Mycobacterium and Corynebacterium
Staphylococcus and Streptococcus
E. coli and Salmonella
Bacillus and Clostridium

Explanation:

Endospores are formed by Bacillus and Clostridium species for survival in harsh conditions.

Q. Endospores are primarily for:
Reproduction
Survival in harsh conditions
Movement
Photosynthesis

Explanation:

Endospores are dormant survival forms, resistant to heat, radiation, and chemicals.

Q. Capsule in bacteria functions primarily to:
Protect against phagocytosis
Produce ATP
Provide motility
Synthesize proteins

Explanation:

Capsules protect bacteria from phagocytosis and aid adherence.

Q. Mesosomes are:
Plasmids
Infoldings of the plasma membrane
Flagellar proteins
Small ribosomes

Explanation:

Mesosomes are infoldings of the plasma membrane in bacteria (functions debated).

Q. Mycobacterium species are:
Acid-fast due to mycolic acid
Without cell walls
Always pathogenic
Gram-positive only

Explanation:

Mycobacteria have waxy cell walls with mycolic acid, making them acid-fast.

Q. Which is NOT a bacterial shape?
Bacilli
Cocci
Spirilla
Amoeboid

Explanation:

Bacterial shapes include cocci, bacilli, spirilla; 'amoeboid' is not a bacterial shape.

Q. Cocci are:
Rod-shaped
Comma-shaped
Spherical
Spiral

Explanation:

Cocci are spherical bacteria.

Q. Bacilli are:
Spiral
Spherical
Comma-shaped
Rod-shaped

Explanation:

Bacilli are rod-shaped bacteria.

Q. Spirilla are:
Spiral-shaped
Spherical
Comma-shaped
Rod-shaped

Explanation:

Spirilla are spiral-shaped bacteria.

Q. Vibrio bacteria are:
Comma-shaped
Rod-shaped
Spherical
Spiral-shaped

Explanation:

Vibrio are comma-shaped bacteria, e.g., Vibrio cholerae.

Q. Conjugation is:
DNA transfer via bacteriophage
Uptake of free DNA
Cell division
DNA transfer via direct contact

Explanation:

Conjugation is bacterial DNA transfer through direct cell-to-cell contact via a sex pilus.

Q. Transformation in bacteria refers to:
Uptake of free DNA
Cell division
DNA transfer via contact
DNA transfer via virus

Explanation:

Transformation is the uptake of free DNA from the environment by competent cells.

Q. Transduction in bacteria refers to:
Cell division
DNA transfer via bacteriophage
Direct cell contact
Uptake of free DNA

Explanation:

Transduction is DNA transfer between bacteria via a bacteriophage (virus).

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