Prokaryotic and Eukaryotic Cells - Microbiology Review (Colleges of Allied Medical Profession, AY 2025-2026)

A comprehensive set of practice questions covering prokaryotic and eukaryotic cell structure, staining, membranes, transport, organelles, and key microbiology concepts from the lecture notes.

How do bacteria primarily divide, and how does this differ from mitosis in eukaryotes?

Bacteria divide by binary fission; they lack spindle fibers and distinct mitotic phases and do not have a nucleus, unlike eukaryotes which divide by mitosis.

Name four common bacterial shapes.

Coccus (spherical), Bacillus (rod-shaped), Vibrio (comma-shaped), Spirillum (spiral).

What term describes cocci arranged in clusters?

Staphylococci.

What term describes cocci arranged in chains?

Streptococci.

What term describes cocci arranged in pairs?

Diplococci.

What does pleomorphism mean in bacteria?

Variation in shape among bacteria; most are monomorphic, a few are pleomorphic.

Give an example of a star-shaped bacterium.

Stella.

Give an example of a rectangular bacterium.

Haloarcula.

What is the protein that makes up most bacterial flagella?

Flagellin.

List the four flagellar arrangements.

Monotrichous, Amphitrichous, Lophotrichous, Peritrichous.

What is bacterial chemotaxis?

Movement toward or away from chemical stimuli, often involving run-and-tumble behavior.

What are endospores and which bacteria form them?

Durable, dormant structures formed by Bacillus and Clostridium species; highly resistant to heat and chemicals.

What does penicillin target in bacteria?

Peptidoglycan synthesis and cross-linking in the cell wall.

What are the features of Gram-positive cell walls?

Thick peptidoglycan layer with teichoic acids; may contain mycolic acids in acid-fast organisms.

What are the features of Gram-negative cell walls?

Thin peptidoglycan layer; outer membrane containing lipopolysaccharide (LPS); periplasmic space; porin proteins.

What are the components of LPS?

Lipid A, a core polysaccharide, and O polysaccharide (endotoxin).

What is the role of porin proteins?

Channel proteins in the outer membrane that allow selective passage of small molecules.

What is periplasm?

Space between the inner (plasma) membrane and the outer membrane in Gram-negative bacteria containing enzymes and other molecules.

What is the Gram stain sequence?

Crystal violet (primary stain) → iodine (mordant) → alcohol decolorizer → safranin (counterstain).

Why does EDTA increase Gram-negative susceptibility to antibiotics?

EDTA chelates divalent cations, destabilizing the outer membrane and increasing permeability to antibiotics.

What is the Fluid Mosaic Model of the cell membrane?

Membranes are viscous, fluid phospholipid bilayers with proteins moving laterally; phospholipids rotate and move; proteins are integrated (integral) or peripheral.

How do prokaryotic and eukaryotic membranes differ in sterol content?

Eukaryotic membranes contain sterols (e.g., cholesterol); prokaryotic membranes typically lack sterols.

Define osmosis and osmotic pressure.

Osmosis is the movement of water across a selectively permeable membrane from higher to lower water concentration; osmotic pressure is the pressure required to stop this movement.

What are isotonic, hypotonic, and hypertonic solutions?

Isotonic: no net water movement; Hypotonic: water moves into the cell; Hypertonic: water moves out, potentially causing plasmolysis or osmotic lysis.

What is active transport and what is group translocation?

Active transport uses energy to move substances against the gradient via a transporter; group translocation uses energy (PEP) to chemically modify the substrate during transport.

What is the difference between prokaryotic cytoplasm and eukaryotic cytoplasm?

Prokaryotes have cytosol and lack a true nucleus; eukaryotes have cytosol and a cytoskeleton, along with membrane-bound organelles.

What is a nucleoid and how does it differ from a nucleus?

Nucleoid is the region in prokaryotes where the chromosome is located; it is not membrane-bound, unlike the true nucleus in eukaryotes.

What evidence supports the endosymbiotic origin of mitochondria and chloroplasts?

Both contain their own DNA and 70S ribosomes, have double membranes, and resemble bacteria, supporting ancient endosymbiosis.

What is the function of rough and smooth endoplasmic reticulum?

Rough ER has ribosomes and synthesizes proteins; smooth ER lacks ribosomes and functions in lipid synthesis and detoxification.

What is the Golgi complex responsible for?

Modifying, sorting, and packaging proteins into secretory vesicles for secretion or delivery to other organelles.

What organelles are involved in degradation and digestion within the cell?

Lysosomes digest macromolecules; peroxisomes break down fatty acids and detoxify reactive oxygen species.

What is the glycocalyx and its roles?

A carbohydrate-rich layer outside the plasma membrane; involved in protection, adherence, and in some bacteria, virulence (capsule).

What are biofilms and why are they important?

Communities of microbes attached to surfaces embedded in extracellular polymeric substances; they are resistant to removal and antibiotics.

What are the main components of plant, algae, and fungal cell walls?

Plants/algae: cellulose; fungi: chitin; bacteria: peptidoglycan (different composition from plant/fungal walls).

What is a eukaryotic cytoskeleton made of?

Microfilaments (actin), intermediate filaments, and microtubules, providing shape, movement, and internal organization.

What are nuclear pores?

Channels in the nuclear envelope that regulate traffic between the nucleus and cytoplasm.

What are the key components of the nucleus?

Chromatin, nucleolus, nuclear envelope, and nuclear pores.

What is the role of mitochondria and chloroplasts in cells?

Mitochondria: cellular respiration and energy production; Chloroplasts: photosynthesis in plants and algae; both have DNA and ribosomes and evidence of endosymbiosis.

What is a capsule in bacteria?

A distinct, gelatinous glycocalyx layer that can aid in virulence and adherence; often visible with special staining techniques.

What is teichoic acid and where is it found?

Teichoic acids are components of the Gram-positive cell wall that contribute to charge and antigenicity.

What is Lipid A?

The endotoxin component of LPS found in the outer membrane of Gram-negative bacteria.

Chromatophores or thylakoids (plasma membrane)

Photosynthetic pigments on foldings