Prokaryotic and Eukaryotic cell structures REVIEW

Differences between prokaryotic and eukaryotic cells

• DNA

  • Prokaryotic: No nucleus, DNA in Nucleoid

  • Eukaryotic: have a membrane bound nucleus used to store DNA

• Cell Wall

  • Prokaryotic: sturdy cell wall made of peptidoglycan

  • Eukaryotic: no peptidoglycan even when they have cell walls

• Internal structures

  • Prokaryotic: no complex membrane bound organelles in cytoplasm

  • Eukaryotic: have membrane bound organelles

Coccus

Circular

Bacillus

Rods

Vibrio

Curved rods

Spirillum

Spiral shaped

Spirochete

Spring shaped

Mono arrangement

Cells completely separated after division (i.e., single cell arrangement)

Staphylo

Irregular clusters

Strepto

Chains

Diplo

Pairs of two cells

Tetrads

Groups of four cells

Sarcina

3D geometrical forms (i.e., cubes)

Bacterial chromosome

• found in the nucleoid region

• Contains essential genetic information for the bacterium (all bacteria have a bacterial chromosome)

Plasmid

• Not present in all bacteria

• Contains non-essential genetic information (i.e., antibiotic resistance, toxin production, etc.)

• Genetic information that bacteria can exchange through the pili appendage

Ribosomes (Prokaryotic)

• site of protein synthesis

• Composed of large and small subunit

  • Large— 50s

  • Small— 30s

  • Together = 70s

Inclusion bodies

Used by bacteria to store excess nutrients

Endospores

• used for protection to allow the bacterium to survive in harsh environments (waste buildup, nutrient depletion etc.)

• Active cells are called Vegetative cells

  • When that feel threatened they induce sporulation and produce endospores to protect their genetic information

Flagella (prokaryotic)

• Motility is primary function

• Smaller (thinner) and less complex

• More numerous

• Move in circular motion

Flagella arrangement

• monotrichous: single flagellum

• Lophotrichous: small bunches from same site

• Amphitrichous: both poles of cell

• Peritrichous: dispersed randomly over surface of cell

Fimbriae (prokaryotic)

• Small, bristle-like fibers sprouting off the surface of many bacterial cells

• Purpose is to allow bacteria to attach to tissues and other surfaces

Pili (prokaryotic)

• tiny hollow projections that attach two bacterial cells and provide a way to exchange genetic information (bacteria have become resistant to antibiotics through this approach)

Glycocalyx (two types) (prokaryotic)

• Slime layer: loose, protects against loss of water (dehydration)

• Capsule: more tightly bound, denser, used to prevent phagocytosis

Gram positive cell envelopes (prokaryotic)

• Thick cell wall; more peptidoglycan

• Stains purple

• Cell wall contains teichoic and lipoteichoic acids

• Lacks an outer cell membrane

Gram negative cell envelopes (prokaryotic)

• Thin cell wall; less peptidoglycan

• Stains pink

• Cell wall does not contain teichoic and lipoteichoic acids

• Has an outer cell membrane with lipoproteins and lipopolysaccharides

What is the purpose of gram stain?

Differentiates bacteria based on the structure of their cell wall

Order of reagents and how they affect stain

• Order of reagents

  • Crystal violet (primary stain)

  • Iodine (mordant)

  • Alcohol (decolorizer)

  • SA Fran in (counterstain)

• Gram positive hold on to crystal violet when rinsed with alcohol due to think cell wall; stain purple

• Gram negative will be stripped of crystal violetwhen rinsed with alcohol due to think cell wall; stain pink after using safranin

Flagella (eukaryotic)

• primary function is motility

• Thicker (9+2 microtubules arrangement) and more complex

• Less numerous

• Move in whip-like motion

Golgi apparatus

• receives protein and lipid filled vesicles from the ER, chemically modifies the contents and ships them to their final location

  • Transitional vesicles from the ER are picked up at the face of GA

  • Proteins are modified by addition of polysaccharides and lipids

  • Condensing vesicles from the GA and are sent to cell membrane, lysosomes, or outside cell

Vacuoles

• purpose is to store anything awaiting digestion

• Will fuse with a lysosome

Lysosome

• contains digestive enzymes that will be used to break down food particles and invading microorganisms (phagocytic cells)

Superficial (human fungal diseases/mycoses)

• affects keratinized tissue in skin, hair, and nails

Subcutaneous (human fungal diseases/mycoses)

• affects skin layer beneath keratinized tissue to the lymph vessels

Systemic (human fungal diseases/mycoses)

• affects internal organs

Opportunistic mycoses

• caused by fungi that only causes disease when the host’s immune system is already weakened