prokaryotic vs. eukaryotic cells

Plasma Membrane

Phospholipid bilayer controlling substance movement.

Cytoplasm

Semi-fluid interior where biochemical reactions occur.

Circular DNA

Unbound chromosome supercoiled within the nucleoid region.

Ribosomes ($70\text{S}$)

Protein-synthesizing complexes.

Cell Wall

Constructed from cross-linked peptidoglycan (murein), a complex polymer formed from amino acids and sugars.

Pili

Surface appendages used for adhesion to external surfaces/cells, and involved in sexual reproduction (bacterial conjugation).

Plasmid

Small autonomous ring of extra-chromosomal DNA.

Capsule

Gelatinous outer layer providing defense against phagocytosis and desiccation.

Mesosome

Infolding of the plasma membrane with various functional roles including photosynthesis in autotrophs and DNA association during binary fission.

Flagellum

Locomotive structural organelle.

Prokaryotic Flagellar Mechanics

Thinner than eukaryotic flagella, driven by chemiosmosis, lacks the $9+2$ microtubule arrangement.

Basal Body

Anchors the flagellar filament to the plasma membrane and peptidoglycan cell wall.

Molecular Motor

Located within the basal body, rotates the shaft.

Hook

Curved flexible joint connecting the basal body motor to the main filament.

Filament

Long helical protein tail projecting outside the cell.

Endosymbiotic Theory

Proposes that eukaryotic organelles evolved from free-living prokaryotic organisms.

Evidence for Endosymbiotic Theory

Mitochondria and chloroplasts contain own circular DNA, small $70\text{S}$ ribosomes, double membranes, and divide independently.