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WorksheetsBasic Concept of Microbiology — MCQ Set
Total questions: 40
Worksheet time: 20mins
Which of the following microorganisms is visible to the naked eye?
Escherichia coli
Staphylococcus aureus
Bread mold
Mycoplasma pneumoniae
The term 'prokaryote' comes from Greek words meaning:
True nucleus
Before nucleus
Hidden cell
Simple cell
The main component of bacterial cell wall is:
Cellulose
Peptidoglycan
Chitin
Lipopolysaccharide
The magnifying power of a microscope is calculated as:
Mobj + Moc
Mobj × Moc
Mobj ÷ Moc
Mobj² + Moc²
The main purpose of heat fixation is to:
Preserve cell morphology
Increase contrast
Improve resolution
Enhance magnification
The Gram-positive bacterial cell wall is characterized by:
Thin peptidoglycan and outer membrane
Thick peptidoglycan and teichoic acids
Absence of peptidoglycan
Presence of lipopolysaccharides
Which of the following organisms lack peptidoglycan in their cell walls?
Fungi
Archaea
Bacteria
Algae
The oil immersion technique increases resolution by:
Increasing focal length
Decreasing the refractive index
Increasing the cone angle of light
Reducing magnification
The function of Braun’s lipoprotein in Gram-negative bacteria is to:
Bind teichoic acid
Anchor outer membrane to peptidoglycan
Regulate membrane transport
Neutralize toxins
Lipopolysaccharide (LPS) in Gram-negative bacteria acts as:
Enzyme substrate
Energy storage
Endotoxin
Transport protein
The Ziehl–Neelsen staining technique is used to detect:
Endospores
Flagella
Acid-fast bacteria
Gram-positive cocci
The basic dye binds best to:
Negatively charged cell components
Neutral cell membranes
Positively charged proteins
Lipid-rich outer membranes
The function of the plasma membrane in bacteria does NOT include:
Respiration
Photosynthesis
Protein synthesis
Nutrient uptake
Archaeal membranes differ from bacterial membranes because they:
Contain sterols like cholesterol
Use ether linkages instead of ester linkages
Are composed mainly of peptidoglycan
Lack phospholipids entirely
The periplasmic space in Gram-negative bacteria contains:
Nucleus and ribosomes
Hydrolytic and transport proteins
Only lipids
DNA and RNA
Which microscope type gives a 3D image of microbial surfaces?
Light microscope
Confocal microscope
Transmission electron microscope
Scanning electron microscope
In the Gram staining procedure, ethanol functions to:
Fix the cells
Act as a mordant
Decolorize cells
Counterstain the cells
The teichoic acids in Gram-positive cell walls contribute to:
Positive surface charge
Membrane permeability
LPS formation
Endotoxin activity
The function of exoenzymes in Gram-positive bacteria is to:
Synthesize proteins
Degrade large nutrients outside the cell
Store energy
Transport ions across membrane
The resolution of a microscope improves when:
Wavelength increases
Cone angle decreases
Refractive index increases
Lens curvature decreases
Which structural feature explains why Gram-negative bacteria are more resistant to antibiotics?
Thick peptidoglycan
Absence of teichoic acids
Presence of an outer membrane
Presence of endospores
Pseudomurein found in some archaea differs from peptidoglycan because:
It contains N-acetylmuramic acid
It uses β(1→4) glycosidic bonds
It has L-amino acids in cross-links
It contains lipid A
The function of hopanoids in bacterial membranes is analogous to:
Cholesterol in eukaryotes
Cellulose in plants
Chitin in fungi
Peptidoglycan in bacteria
Archaeal S-layer serves primarily to:
Store energy
Provide structural support and protection
Carry out photosynthesis
Facilitate motility
During Gram staining, Gram-positive cells retain crystal violet because:
The dye forms ionic bonds with LPS
Alcohol dehydrates thick peptidoglycan
Teichoic acids bind the dye strongly
Safranin blocks decolorization
Confocal laser microscopy is particularly useful for studying:
Viral morphology
Biofilm structures
Archaeal motility
Gram staining patterns
Which of the following structures is not membrane-bound in eukaryotic cells?
Ribosome
Mitochondrion
Lysosome
Golgi apparatus
In electron microscopy, the higher resolution is due to:
Use of light with shorter wavelengths
Use of magnetic lenses and electron beams
Higher magnification alone
Use of immersion oil
The permeability barrier function of LPS is primarily due to:
Lipid A region
O-side chain
Core polysaccharide
Porin proteins
The Gram-negative outer membrane is connected to peptidoglycan via:
Teichoic acids
Hopanoids
Braun’s lipoprotein
Adhesion pili
Which of the following statements best explains why acid-fast bacteria resist decolorization by acid-alcohol?
They have a thick peptidoglycan layer that traps crystal violet.
Their cell wall contains large amounts of mycolic acids and waxes.
The basic fuchsin dye binds covalently to teichoic acids.
They possess an outer membrane composed of LPS.
During chemical fixation, glutaraldehyde and formaldehyde preserve cell structures primarily by:
Precipitating cell wall polysaccharides.
Cross-linking proteins and lipids.
Dehydrating cytoplasmic material.
Reacting with nucleic acids only.
In the Gram staining mechanism, why does alcohol treatment increase the porosity of Gram-negative bacteria?
It hydrolyzes the teichoic acids.
It extracts lipids from the outer membrane.
It disrupts peptide interbridges.
It denatures cytoplasmic proteins.
Teichoic acids are absent in Gram-negative bacteria because:
They would disrupt LPS synthesis.
Their outer membrane performs a similar structural role.
They are replaced by pseudomurein.
They are destroyed by lipases in the periplasm.
The energy conservation functions observed in the periplasmic space of Gram-negative bacteria are often associated with:
Chemolithotrophic metabolism and electron transport chains.
Photosynthetic pigment localization.
Peptidoglycan cross-link synthesis.
DNA replication machinery.
Which of the following best distinguishes Archaeal plasma membranes from bacterial membranes?
They contain glycerol connected to fatty acids via ester linkages.
They have linear hydrocarbon chains.
Their hydrocarbons are branched and connected to glycerol by ether bonds.
They lack phospholipid bilayers entirely.
The S-layer in Archaea differs functionally from bacterial peptidoglycan because it:
Contains L-amino acids and provides enzymatic activity.
Serves as a protein-based structural lattice and protective barrier.
Is lipid-based and regulates osmotic pressure.
Contains both DNA and RNA-binding proteins.
The resolution in microscopy can be improved by all of the following EXCEPT:
Increasing the refractive index of the medium.
Using light of shorter wavelength.
Decreasing the numerical aperture of the objective.
Increasing the cone angle of illumination.
Lipopolysaccharide (LPS) contributes to Gram-negative pathogenicity primarily by:
Acting as an endotoxin through the lipid A component.
Facilitating nutrient uptake via the O-side chain.
Stabilizing the cytoplasmic membrane.
Neutralizing acidic environments.
In confocal scanning laser microscopy, what is the key advantage of using a pinhole aperture above the objective lens?
It increases magnification by splitting light beams.
It allows only in-focus light from a specific plane to form the image.
It enhances color differentiation between fluorophores.
It compensates for light diffraction at high wavelengths.
