Chapter 4 Functional Anatomy of Prokaryotic Cells (CH 4: 4.1–4.5 & 4.12)

Vocabulary-style flashcards covering the major prokaryotic cell structures, differences with eukaryotes, and key concepts from CH 4.

Prokaryotes

Single-celled organisms in the domains Bacteria and Archaea that lack a membrane-bound nucleus and other membrane-bound organelles.

Bacteria & Archaea

The two primary domains comprising prokaryotes.

Pleomorphic

Describes bacteria that can have different shapes or lack a single definite shape.

Cocci

Spherical bacterial cells.

Bacilli

Rod-shaped bacterial cells.

Vibrio

Curved, comma-shaped bacterium.

Spirillum volutans

A spiral-shaped bacterium.

Glycocalyx

Extracellular layer of polysaccharide and/or protein; includes capsules and slime layers; aids adherence and protection; forms biofilms.

Capsule

Well-organized, tightly attached glycocalyx surrounding some bacteria; often a virulence factor.

Slime layer

Looser, unorganized glycocalyx that is more diffuse around the cell.

Biofilm

Multi-cell bacterial communities embedded in an exopolysaccharide matrix.

Virulence factor

A trait that enables a microbe to cause disease, often including capsules or adhesins.

Flagellum

Rotary motility structure (propeller-like) that enables bacterial movement; composed of filament, hook, and basal body.

Flagellin

Protein subunits that make up the bacterial flagellar filament.

Basal body

The motor-anchoring structure inserted in the cell wall/plasma membrane that drives flagellar rotation.

Hook

CONNECTS the flagellar filament to the basal body.

Axial filaments

Flagella-like structures in spirochetes located between the cell wall and an outer sheath; produce corkscrew motion.

Spirochete

A corkscrew-shaped bacterium with axial filaments.

Chemotaxis

Movement toward or away from chemical stimuli; guided by chemical attractants or repellents.

Phototaxis

Movement toward or away from light.

Fimbriae

Short, hair-like appendages on bacteria used mainly for attachment to surfaces; many per cell.

Pili

Longer, fewer appendages used for attachment and DNA transfer (conjugation) via the sex pilus; may enable twitching motility.

Conjugation

DNA transfer between bacteria through direct contact via a sex pilus.

Twitching motility

A type of bacterial movement mediated by pili retraction.

Gliding motility

Smooth, flagellum-independent movement over surfaces observed in some bacteria.

Gram-positive bacteria

Bacteria with a thick peptidoglycan cell wall and teichoic acids; no outer membrane.

Gram-negative bacteria

Bacteria with a thin peptidoglycan layer and an outer membrane containing LPS; periplasmic space between membranes.

Acid-fast bacteria

Bacteria with waxy, lipid-rich cell envelopes (mycolic acids) that retain stains after acid wash.

Mycoplasma

Bacteria that naturally lack a cell wall.

Archaea cell wall (pseudomurein)

Archaeal cell wall made of pseudomurein rather than peptidoglycan.

Mycobacteria

Bacteria with waxy mycolic acids in their envelope; acid-fast; resistant to many chemicals.

Mycolic acids

Long-chain fatty acids in mycobacterial envelopes contributing to acid-fastness and resistance.

Plasma membrane

Phospholipid bilayer with integral and peripheral proteins; selective permeability.

Simple diffusion

Passive movement of small, nonpolar molecules down their concentration gradient.

Facilitated diffusion

Passive transport via membrane proteins (no energy required).

Osmosis

Diffusion of water across a semipermeable membrane toward higher solute concentration.

Active transport

Energy-requiring transport moving substances against their concentration gradient.

Aquaporins

Membrane channels that facilitate rapid osmosis.

Nucleoid

An irregularly shaped region containing the bacterial chromosome; not membrane-bound.

Ribosomes (70S)

Sites of protein synthesis in prokaryotes; composed of rRNA and proteins; smaller than eukaryotic ribosomes.

Plasmids

Small, circular DNA molecules that replicate independently; carry nonessential genes.

Inclusions

Cytoplasmic storage bodies or specialized structures (e.g., PHB granules, volutin, glycogen).

PHB granules

Polyhydroxybutyrate lipid inclusions used for storage.

Metachromatic granules (volutin)

Polyphosphate storage granules in some bacteria.

Glycogen granules

Polysaccharide storage granules.

Magnetosomes

Magnetite-containing inclusions that enable magnetotaxis.

Magnetotaxis

Movement along magnetic field lines due to magnetosomes.

Gas vacuoles

Protein-bound inclusions that provide buoyancy in aquatic bacteria.

Chromatophores

Membrane infoldings containing pigments and enzymes for photosynthesis.

Carboxysomes

Protein-covered bodies containing Rubisco for CO2 fixation.

Endospore

Dormant, highly resistant dormant cell form produced by Bacillus and Clostridium under stress.

Sporulation

Process of endospore formation in response to nutrient limitation.

Germination

Endospore to vegetative cell reversion when conditions are favorable.

Dipicolinic acid (DPA) and Ca2+

Molecules that stabilize endospores by reducing water content.

Protoplast

Cell that has had its wall removed (lysozyme treatment).

Spheroplast

Bacterium with partial cell wall removal, retaining a plasma membrane

L-forms

Bacteria that lack a cell wall and can grow and divide in this wall-deficient state.

Endosymbiont theory

Hypothesis that eukaryotic organelles originated from symbiotic bacteria (mitochondria and chloroplasts).

Mitochondria and chloroplasts

Organelles derived from ancient bacteria; contain circular DNA and 70S-like ribosomes.

Evidence for endosymbiotic theory

Mitochondria/chloroplasts resemble bacteria in size, DNA type, ribosomes, and replication; sensitive to antibiotics that affect bacteria.

Nucleoid vs nucleus

Nucleoid: region of prokaryotic DNA; nucleus: membrane-bound organelle in eukaryotes.

Teichoic acids

Negatively charged polymers in Gram-positive cell walls; include lipoteichoic and wall teichoic acids.

Lipid A

Endotoxin component of LPS in Gram-negative outer membrane.

O polysaccharide (O antigen)

Variable polysaccharide chain in LPS; determines antigenic differences among Gram-negative bacteria.

Porins

Protein channels in the outer membrane of Gram-negative bacteria allowing diffusion of small molecules.

Periplasmic space

The space between the inner (plasma) membrane and outer membrane in Gram-negative bacteria.

Peptidoglycan

Mesh-like polymer of sugars (NAG-NAM) and short peptides forming the bacterial cell wall sacculus.

Penicillin mechanism

Antibiotic that inhibits formation of peptide cross-bridges in peptidoglycan, weakening the cell wall.

N-acetylglucosamine (NAG)

Sugar component of peptidoglycan.

N-acetylmuramic acid (NAM)

Sugar component of peptidoglycan that carries peptide chains.

Peptide cross-bridge

Peptide bonds linking glycan strands in peptidoglycan; target of beta-lactam antibiotics.

Sacculus

The rigid bacterial cell wall formed by the peptidoglycan network.

Lipid A endotoxin

Toxic component of LPS released upon cell lysis; triggers strong immune responses.

Gram staining relevance

A scheme that categorizes bacteria by cell wall properties (Gram-positive vs Gram-negative) useful for diagnosis and therapy.

Outer membrane

Extra membrane in Gram-negative bacteria containing LPS and porins.

Inner membrane

Plasma membrane of bacteria separating cytoplasm from periplasm.

Pseudomurein

Cell wall component found in some Archaea, similar in function to peptidoglycan but chemically distinct.

Capsule vs slime layer distinction

Capsule: organized, tightly bound glycocalyx; slime layer: loose, unorganized coating.

Endospore resistance

Endospores resist heat, radiation, chemicals due to low water content and protective molecules like DPA.

Endospore germination

Process by which a dormant endospore returns to vegetative growth when conditions improve.

Model of a bacterial cell

A schematic representation showing the prokaryotic cell envelope, nucleoid, ribosomes, inclusions, and external structures.

Bacterial nucleoid size range

Approximately 500,000 to 5,000,000 base pairs in length.