Functional Anatomy of Prokaryotic and Eukaryotic Cells

Vocabulary flashcards covering key terms from the lecture on prokaryotic and eukaryotic cell anatomy.

Prokaryote

Cell type with no nucleus; DNA is a single circular chromosome not surrounded by a membrane.

Eukaryote

Cell type with a true, membrane-bound nucleus and membrane-bound organelles.

Binary fission

Asexual reproduction method in which a prokaryotic cell divides into two identical cells.

Peptidoglycan

Bacterial cell-wall polymer composed of NAG and NAM sugars cross-linked by peptides.

Histones

DNA-binding proteins found in eukaryotic chromosomes but absent in typical bacteria.

Organelles

Specialized, membrane-bound structures in eukaryotic cells (e.g., mitochondria, ER).

Cocci

Spherical bacterial shape.

Bacilli

Rod-shaped bacterial cells.

Vibrio

Curved, comma-shaped bacterium.

Spirillum

Rigid, helical bacterial shape with external flagella.

Spirochaete

Flexible, corkscrew-shaped bacterium with internal (axial) flagella.

Monomorphic

Having a single, constant cell shape (most bacteria).

Pleomorphic

Ability of some bacteria to alter shape or size in response to environmental conditions.

Glycocalyx

Sticky, extracellular polysaccharide layer outside the cell wall; includes capsules and slime layers.

Capsule

Organized, firmly attached glycocalyx that inhibits phagocytosis.

Slime layer

Unorganized, loosely attached glycocalyx that aids surface attachment.

Flagella

Long, whip-like appendages for bacterial motility, built from flagellin.

Flagellin

Protein subunit forming bacterial flagellar filaments.

Basal body

Motor structure anchoring flagellum to cell wall and plasma membrane.

Monotrichous

Single flagellum at one pole of a bacterium.

Amphitrichous

Single flagellum at each pole.

Lophotrichous

Tuft of flagella at one or both poles.

Peritrichous

Flagella distributed over the entire cell surface.

Taxis

Directed movement toward or away from stimuli (chemotaxis, phototaxis, etc.).

H antigen

Flagellar protein antigen used to distinguish bacterial serovars (e.g., E. coli O157:H7).

Axial filament

Internal endoflagella of spirochetes; rotation produces corkscrew motility.

Fimbriae

Numerous, short, hair-like appendages that enable bacterial attachment to surfaces.

Pili

Longer appendages that mediate DNA transfer (conjugation) between bacterial cells.

Cell wall

Rigid structure outside plasma membrane; prevents osmotic lysis; made of peptidoglycan in bacteria.

Teichoic acid

Polymer in Gram-positive walls; includes wall and lipoteichoic acids; regulates cation movement and provides antigenic specificity.

Lipoteichoic acid

Teichoic acid variant that anchors peptidoglycan to the plasma membrane.

Wall teichoic acid

Teichoic acid linked to peptidoglycan layers.

Gram-positive cell wall

Thick peptidoglycan layer with teichoic acids; no outer membrane.

Gram-negative cell wall

Thin peptidoglycan, no teichoic acid, outer membrane containing LPS.

Outer membrane

Extra lipid bilayer in Gram-negative bacteria containing lipopolysaccharide, lipoproteins, and porins.

Lipopolysaccharide (LPS)

Molecule of Gram-negative outer membrane composed of lipid A, core polysaccharide, and O polysaccharide.

Lipid A

Endotoxin component of LPS responsible for fever and shock.

O Polysaccharide

Antigenic sugar side chain of LPS used for serotyping (e.g., O157).

Porin

Protein channel in Gram-negative outer membrane allowing passage of small molecules.

Gram stain mechanism

CV-I complexes retained in thick Gram-positive walls; washed out of thin Gram-negative walls after alcohol step.

Mycolic acid

Waxy lipid in acid-fast bacteria (e.g., Mycobacterium) that resists Gram staining.

Lysozyme

Enzyme that hydrolyzes peptidoglycan disaccharide bonds, weakening bacterial walls.

Penicillin

Antibiotic that blocks peptide cross-bridge formation in peptidoglycan.

Protoplast

Wall-less form of a Gram-positive cell after enzymatic removal of peptidoglycan.

Spheroplast

Wall-less form of a Gram-negative cell; outer membrane may remain.

L-form

Bacteria that have lost their cell wall and assume irregular shapes; can arise naturally or after antibiotics.

Plasma membrane

Phospholipid bilayer with peripheral and integral proteins; site of ATP synthesis in prokaryotes.

Fluid Mosaic Model

Concept that membrane lipids and proteins move laterally, giving the membrane fluidity.

Simple diffusion

Net movement of molecules from high to low concentration without energy input or transporter proteins.

Facilitated diffusion

Passive movement of solutes down their gradient via specific membrane transporter proteins.

Osmosis

Diffusion of water across a selectively permeable membrane toward higher solute concentration.

Osmotic pressure

Pressure needed to stop osmotic water flow.

Isotonic solution

External solute concentration equal to cytoplasm; no net water movement.

Hypotonic solution

Lower external solute concentration; water enters cell, risking osmotic lysis.

Hypertonic solution

Higher external solute concentration; water leaves cell, causing plasmolysis.

Active transport

Energy-dependent movement of substances against their concentration gradient using transporter proteins and ATP.

Group translocation

Prokaryotic transport that chemically modifies a substance (using PEP) during its passage across the membrane.

Cytoplasm

Substance inside plasma membrane; in eukaryotes, outside the nucleus.

Nucleoid

Irregularly shaped region in prokaryotes containing the chromosome; not membrane bound.

Ribosome

Site of protein synthesis composed of rRNA and proteins.

70S ribosome

Prokaryotic ribosome (30S + 50S subunits); also in mitochondria and chloroplasts.

80S ribosome

Eukaryotic cytoplasmic ribosome (40S + 60S subunits) attached to ER or free in cytosol.

Inclusions

Reserve deposits such as volutin, polysaccharide, lipid, sulfur granules, carboxysomes, gas vacuoles, magnetosomes.

Endospore

Dormant, highly resistant bacterial structure formed by Bacillus and Clostridium species.

Sporulation

Process of endospore formation under adverse conditions.

Germination

Return of an endospore to its vegetative state when conditions improve.

Serial Endosymbiosis Theory

Hypothesis that mitochondria and chloroplasts evolved from prokaryotes living within ancestral host cells.

Endocytosis

Eukaryotic membrane process that brings substances into the cell.

Phagocytosis

Endocytosis in which pseudopods engulf large particles or microbes.

Pinocytosis

Endocytosis of fluid and dissolved substances via membrane invagination.

Cytoskeleton

Network of microfilaments, intermediate filaments, and microtubules that supports eukaryotic cell shape and transport.

Cytoplasmic streaming

Movement of cytoplasm that distributes nutrients and organelles within some eukaryotic cells.

Mitochondrion

Eukaryotic organelle where cellular respiration occurs; contains its own 70S ribosomes and DNA.

Chloroplast

Photosynthetic organelle in plants and algae; contains thylakoids, chlorophyll, and 70S ribosomes.