OBJ - Bacterial Structure & Function

Question 1

Prokaryote properties

Answer 1

Smaller
Lack nuclei & membrane bound organelles/receptors
Incapable of endocytosis
Different small ribosomes (70S) & lipids
Simple appendages (2 proteins)
Circular DNA, no histones 
Plasmids - circles of DNA not in circular DNA
Complex Cell wall & glycocalyx
No cytoskeleton
Binary fission

Question 2

Prokaryote Organelles

Answer 2

Cell/Cytoplasmic membrane see Gram – vs Gram +; inner membrane = gate keeper (lacks sterols)

Cell wall made of murein/peptidoglycan (same thing)

Outer membrane resides outside cell wall & is the external layer of the bilayer
Made up of Lipopolysaccharide (LPS) – only for Gram NEGATIVE
Structure: Lipid A, Core polysaccharide & repeating O antigen (hydrophilic)
Importance endotoxin & illicits strong immune response
Binds to monocytes, dendritic cells, macrophages and B Cells

Target Cell wall penicillin
Interfere with bacterial enzymes sulfonamides
Target Protein synthesis Tetracycline
Creates Periplasmic space/periplasm

Capsule carb/protein layers for protection in harsh environments/survival; (both Gram +/-)
polysaccharide layer outside envelope, OUTSIDE of LPS
-interferes with compliment deposition onto the membrane so can’t flag to be phagocytosed

Question 3

Prokaryotes Appendages

Answer 3

Flagella used for mobility – either runs (CCW) or tumbles (CW)
**Not genetically like eukaryotic flagella/cilia

Pili/fimbriae used for attachment/genetic transfer, small & hairlike

Question 4

Cell Envelope: Gram +

Answer 4

VIOLET (Crystal Violet)
Retain violet color because of THICK peptidoglycan cell wall
More receptive to antibiotics
Cell Envelope (internal to external)

THICH cell wall of peptidoglycan
Same lipid bilayer inner membrane

spores = Gram + b/c thick biofilm layer

Teichoic Acid often seen in cell wall

Question 5

Cell Envelope: Gram -

Answer 5

PINK (Safranin)
Do not retain crystal violet because of THIN peptidoglycan layer in periplasm

Outer membrane removed by ETOH wash -> gets washed away

Harder to kill with antibiotics - impermeable lipid based outer membrane

Triggers INNATE immune response to produce cytokines & inflammation– high temp, high RR, low BP and can lead to shock/sepsis

Cell Envelope (internal to external)
Same lipid bilayer inner membrane
Cell Wall Thin peptidoglycan layer (periplasm)
Outer membrane made of LPS (Lipid A, polysaccharide & O antigen tails)
Porins – molecular channels
Capsule

** LPS’s Lipd A is the toxic part

Question 6

Cell Envelope: Mycobacteria

Answer 6

Acid-Fast Bacteria - don’t gram stain because resist decolorization by acids (bright red cells against blue background/cells)

No outer membrane like Gram negative but significant peptidoglycan cell wall

External permeability barrier
“pseudoperiplasm”

Cause tuberculosis & leprosy

Question 7

Cell Envelope: Mycoplasma

Answer 7

Refers to the genus Mycoplasma

Lacks cell wall

Intracellular parasite
Unaffected by common antibiotics (penicillin/beta-lactams)

Question 8

Antibiotics

Answer 8

• Gyrase Topisomerases targets DNA Gyrase (uncoils Bacterial DNA)
• Bacterial Ribosome
• Bacterial Cell wall - ceflex, vanco, penicillin, bacitracin inhibits cell wall synthesis (Gram+/-)
  trasnglycosidation = vanco inhibits formation
  transpeptidation = penicillin inhibits formation

Question 9

Know these INTERNAL structures

Answer 9

Chromosome
usually only one
haploid (single copy of double-stranded DNA)
no histone proteins encasing it
no nuclear membrane (no nucleus)

Plasmids =self-replicating DNA in cytoplasm – often
capable of transfer to other cells

Ribosomes –differ from eukaryotic ribosomes

• there is no ER or golgi
• protein synthesis proceeds right after
• transcription in cytoplasm

Inner membrane: where respiration takes place in
bacteria

Spores – Aberrant daughter cells with thick
protective cell wall

Question 10

Know these SURFACE structures

Answer 10

Peptidoglycan
– Disaccharide backbone
– Peptide cross linking

Outer membrane (Gram – only)

Flagella
– anchored in cell wall
– get energy from inner (cell) membrane

Pili (also called Fimbriae)
– Aggregation
– Attachment
– Sex

Capsules