Prokaryotic Cell Structure and Function

Prokaryotic DNA structure

Unicellular, circular DNA lacking a true membrane-bound nucleus.

Bacterial cell membrane sterols

Bacteria use hopanoids for membrane reinforcement instead of cholesterol.

Peptidoglycan cell wall

Made of sugars and amino acids; provides cell shape, rigidity, and protection.

Gram-positive cell wall

Features a thick peptidoglycan layer threaded by negatively charged teichoic acids.

Gram-negative cell wall

Features a thin peptidoglycan layer and a bi-layer outer membrane with LPS.

Lipopolysaccharide (LPS)

An endotoxin in Gram-negative outer membranes that can cause a cytokine storm.

Capsule function

Protects the cell, aids surface adhesion, and helps evade immune cells.

Acid-fast bacteria cell walls

Contain waxy mycolic acids that protect against toxic substances.

Fimbriae

attach to surfaces

motility

fuzzy

Nucleoid

The non-membrane-bound region where bacterial genetic material is organized.

genetic control center

Plasmids

Extrachromosomal DNA carrying genes for antibiotic resistance and toxins.

pili transfer

Prokaryotic ribosomes

Complete 70S ribosomes composed of a 30S small subunit and 50S large subunit

Sites of protein synthesis

Translates mRNA into protein

Endospores

Dehydrated, dormant, highly resistant structures formed by some Gram-positive bacteria.

Bacterial flagella parts

Composed of a basal body, a hook, and a filament made of flagellin.

Chemotaxis

Bacterial movement dependent on chemical gradients

Cytoplasm

Water, Essential ions

Small organic molecules/metabolites Macromolecules

Pili

sex pili transfer DNA between cells.

thin and long

Membrane Proteins

Structural support

Detection/release of signals

Secretion of virulence factors

Ion Transport

Differential Staining

Distinguishing microbes based on staining properties.

Gram stain

cell wall

Acid fast stain

lipid content

Endospore stain

spores

Cell wall

Osmotic pressure protection

Made of Peptidoglycan

Efflux pumps, mycolic acids

Plasma Membrane

Semi-permeable

Protein transporters, porins etc.

Hopanoids

membrane reinforcement for plasma

Vegetative cell characteristic

Sensitive to extreme temps & radiation

Mostly Gram-positive

Normal water content and enzymatic activity

Capable to active growth

Endospore

Resistant to extreme temps & radiation

Do not absorb Gram stain; only some endospore stains

Dehydrated; no metabolic activity

Dormant; no growth

Flagellum

Motility - External filament that propels the cell.

Hook

connects filament to base

Basal body

Protein complex drives motor rotation

Phototaxis

bacterial movement in response to light