Student Learning Objectives - Chapter 4

SLO 1: Plasma (Cell) Membrane - Structure and Function

Phospholipid bilayer with embedded proteins (fluid mosaic model); selectively permeable barrier that controls transport of nutrients and wastes, and serves as the site for metabolic and energy reactions.

SLO 1: Bacterial Cell Wall - Structure and Function

Rigid layer composed of peptidoglycan (glycan chains cross-linked by short peptides); determines cell shape and prevents osmotic lysis from shifting pressures.

SLO 1: Bacterial Capsule - Structure and Function

Highly organized, dense glycocalyx tightly attached to the cell wall; protects against dehydration, aids in biofilm formation, blocks phagocytosis by white blood cells, and increases virulence.

SLO 1: Bacterial Flagella - Structure and Function

External protein appendage anchored into the cell envelope; rotates 360 degrees to provide cellular motility (self-propulsion) through fluid environments.

SLO 1: Bacterial Pili - Structure and Function

Rigid tubular structures made of pilin protein found in Gram-negative bacteria; function in bacterial conjugation (transfer of genetic material/DNA) and surface adherence.

SLO 1: Bacterial Fimbriae - Structure and Function

Fine, short, numerous hair-like protein bristles emerging from the cell surface; function primarily in adherence to surfaces and other cells to facilitate colonization and biofilms.

SLO 1: Axial Filament (Periplasmic Flagella) - Structure and Function

Internal flagella bundles enclosed between the cell wall and outer sheath in spirochetes (e.g., Treponema pallidum); contract and flex to produce a twisting, corkscrew-like motility.

SLO 1: Bacterial Cytoplasm - Structure and Function

Dense gelatinous solution (70-80% water) dissolved with sugars, amino acids, salts, and vitamins; acts as a solvent and metabolic pool housing raw materials for cellular processes.

SLO 1: Bacterial Ribosomes - Structure and Function

70S ribonucleoprotein complexes made of 60% rRNA and 40% protein (50S large and 30S small subunits); serve as the universal sites of protein synthesis (translation).

SLO 1: Bacterial Nucleoid - Structure and Function

Non-membrane-bound central area of the cytoplasm housing the chromosome; contains the single, circular, double-stranded DNA molecule that holds all essential hereditary instructions.

SLO 1: Plasmids - Structure and Function

Small, circular, double-stranded extrachromosomal DNA units; replicate independently and encode adaptive traits like antibiotic resistance and virulence factors, and are used in genetic engineering.

SLO 1: Cell Inclusions and Granules - Structure and Function

Intracellular storage bodies that vary in size, number, and content; store organic nutrients (glycogen, PHB) or inorganic compounds (polyphosphate, sulfur) for use during starvation.

SLO 2: Fluid Mosaic Model - Structural Description

Phospholipid bilayer where hydrophilic phosphate heads face outward and hydrophobic fatty acid tails face inward, with proteins embedded throughout (mosaic) that move laterally within the plane (fluid).

SLO 3: Gram-Positive Cell Wall - Key Characteristics

Thick peptidoglycan layer (20 to 80 nm) containing teichoic acid and lipoteichoic acid; single major layer; lacks an outer membrane and LPS; narrow periplasmic space; more penetrable.

SLO 3: Gram-Negative Cell Wall - Key Characteristics

Thin peptidoglycan layer (8 to 11 nm) surrounded by an asymmetric outer membrane containing lipopolysaccharide (LPS endotoxin) and porins; extensive periplasmic space; less penetrable.

SLO 3: Teichoic and Lipoteichoic Acid - Location and Functions

Found exclusively in Gram-positive cell walls; function in cell wall maintenance, enlargement during cell division, cation movement across the envelope, and immune stimulation.

SLO 3: Lipopolysaccharide (LPS) - Location and Function

Found in the outer leaflet of Gram-negative outer membranes; consists of lipid A (endotoxin) which can trigger fever and shock, polysaccharide chains that act as receptors, and immune evasion structures.

SLO 3: Porin Proteins - Location and Function

Transmembrane protein channels located exclusively in the Gram-negative outer membrane; regulate and permit the passage of small molecules into and out of the cell.

SLO 4: Atrichous Bacteria

Bacteria that completely lack flagella and are non-motile by flagellar mechanisms.

SLO 4: Monotrichous Bacteria

Bacteria possessing a single flagellum located at one pole (end) of the cell.

SLO 4: Amphitrichous Bacteria

Bacteria with flagella positioned at both opposite poles of the cell (single flagellum or tufts at each end).

SLO 4: Lophotrichous Bacteria

Bacteria possessing small clusters, bunches, or tufts of flagella emerging from a single site or pole.

SLO 4: Peritrichous Bacteria

Bacteria with flagella dispersed randomly and uniformly all over the entire outer perimeter and surface of the cell.

SLO 5: Define Glycocalyx

A general term for any coating of macromolecules (polysaccharides and/or proteins) positioned external to the bacterial cell wall.

SLO 5: Define Slime Layer

A loose, non-uniform, soluble glycocalyx shield that is weakly attached to the cell wall; prevents desiccation and aids in surface attachment.

SLO 5: Define Capsule

A dense, highly structured, gelatinous glycocalyx layer that is bound tightly to the cell wall; prevents phagocytosis by host white blood cells and increases virulence.

SLO 6: Prokaryotic vs. Eukaryotic Flagella

Prokaryotic flagella are naked, non-membrane-bound fibers of flagellin protein that rotate 360 degrees via a basal motor; eukaryotic flagella are membrane-sheathed 9+2 microtubule doublets (tubulin) that undulate in a whip-like motion powered by ATP.

SLO 6: Prokaryotic vs. Eukaryotic Ribosomes

Prokaryotic ribosomes are 70S (composed of 50S large and 30S small subunits); eukaryotic ribosomes are 80S (composed of 60S large and 40S small subunits), which are larger and contain more proteins and rRNA.

SLO 7: Two Types of Cell Inclusions - Organic vs. Inorganic

Organic inclusions store organic polymers for energy and carbon (e.g., glycogen granules, PHB droplets, or gas vacuoles for buoyancy); Inorganic granules store inorganic compounds (e.g., volutin/polyphosphate granules for ATP synthesis, or sulfur granules).

SLO 8: Define Endospore

A dormant, dehydrated, metabolically inert survival structure with a thick protein coat produced by certain Gram-positive bacteria to survive extreme heat, drying, freezing, radiation, and chemicals.

SLO 8: Define Sporulation

The developmental cycle of converting a metabolically active vegetative cell into an inert endospore upon encountering harsh environmental conditions or nutrient starvation (survival mechanism, not reproduction).

SLO 8: Define Germination

The process where a dormant endospore returns to an actively metabolizing, reproducing vegetative cell when exposed to favorable moisture, warmth, and chemical nutrients.

SLO 9: Two Major Genera of Endospore-Forming Bacteria

Bacillus (aerobic, spore-forming rods, e.g., Bacillus anthracis) and Clostridium (anaerobic, spore-forming rods, e.g., Clostridium tetani, Clostridium botulinum).