Introduction to Prokaryotic Cells – Core Vocabulary

These vocabulary flashcards highlight the essential terms and definitions from the lecture on prokaryotic cell structure, classification, and clinically significant features.

Prokaryote

Unicellular organism lacking a membrane-bound nucleus and organelles; domains Bacteria and Archaea.

Bacteria

Domain of prokaryotes whose cell walls contain peptidoglycan.

Archaea

Domain of prokaryotes with pseudopeptidoglycan cell walls and branched-chain membrane lipids.

Monomorphic Bacteria

Species that maintain a single, constant cell shape.

Pleomorphic Bacteria

Species capable of adopting multiple shapes or forms.

Binary Fission

Asexual reproduction in prokaryotes where the chromosome is copied and the cell splits into two daughter cells.

Plasma Membrane

Thin, flexible phospholipid bilayer acting as a selective barrier around all cells.

Membrane Fluidity

Flexibility of the plasma membrane, influenced by temperature and fatty-acid saturation.

Lipid Monolayer

Heat-adapted archaeal membrane composed of fused phospholipids forming a single layer.

Peptidoglycan

Protein-sugar polymer forming the rigid bacterial cell wall.

Pseudopeptidoglycan

Archaeal cell-wall polymer analogous to peptidoglycan.

Gram-Positive Bacterium

Bacterium with a thick peptidoglycan cell wall, no outer membrane; stains purple.

Gram-Negative Bacterium

Bacterium with a thin peptidoglycan layer, outer membrane with lipopolysaccharide; stains pink.

Porin

Protein channel in Gram-negative outer membrane allowing small molecules to pass.

Teichoic Acid

Gram-positive cell-wall polymer that stabilizes the wall, maintains shape, and aids cation transport.

Lipopolysaccharide (LPS)

Endotoxin-containing molecule in Gram-negative outer membrane; includes lipid A.

Acid-Fast Staining

Diagnostic stain detecting mycolic-acid–rich cell walls, yielding red/pink cells.

Mycolic Acid

Waxy lipid in cell walls of Mycobacterium and Nocardia that slows nutrient uptake and growth.

Mycoplasma

Wall-less, sterol-stabilized, pleomorphic bacteria that live intracellularly.

L-Form Bacteria

Variants that lost their cell wall; resist wall-targeting antibiotics and some stresses.

Flagellum

Filamentous motility organelle powered by a rotary motor in many bacteria.

Run-and-Tumble

Flagellar movement pattern enabling directional changes in response to stimuli.

Chemotaxis

Bacterial movement toward or away from chemical cues.

Phototaxis

Bacterial movement in response to light.

Aerotaxis

Bacterial movement influenced by oxygen concentration.

Monotrichous

Single polar flagellum arrangement.

Lophotrichous

Cluster (tuft) of flagella at one pole.

Amphitrichous

Single or tufted flagella present at both poles.

Peritrichous

Flagella distributed over the entire cell surface.

Periplasmic Flagella (Axial Filaments)

Internal flagella in spirochetes enabling corkscrew motility.

Fimbria

Short, bristle-like adhesin appendage aiding surface attachment and biofilm formation.

Pilus

Longer, fewer surface appendage used for adhesion, motility, and DNA transfer (conjugation).

Glycocalyx

Carbohydrate-rich external layer that aids adhesion, prevents desiccation, and hinders antimicrobials.

Slime Layer

Loose, unorganized glycocalyx variant.

Capsule

Tightly organized glycocalyx providing strong protection and virulence.

Nucleoid

Region containing the single, circular prokaryotic chromosome.

Ribosome (70S)

Prokaryotic RNA-protein complex (50S + 30S) that synthesizes proteins.

Endospore

Dormant, highly resistant bacterial structure formed under stress.

Sporulation

Process by which a vegetative cell forms an endospore, packaging DNA and protective layers.

Bacillus anthracis

Gram-positive, spore-forming pathogen causing anthrax.

Clostridium difficile

Spore-forming anaerobe responsible for antibiotic-associated severe diarrhea.