Microbiology Flashcards
what are the 4 major groups of human pathogens and what cell type are they?
protozoa - eukaryotes
fungi - eukaryotes
bacteria - prokaryotes
viruses - obligate parasites
what is the size difference between prokaryotes and eukaryotes?
eukaryotes are 5-10 times bigger than prokaryotes
how does DNA in prokaryotes compare to that of eukaryotes?
single circular chromosome rather that linear chromosomes and histones
prokaryotes contain cell walls T/F
True aka peptidoglycan
what are the structural components of a prokaryotic cell?
- plasma membrane
- cell wall (peptidoglycan)
- Nucleoid (DNA and associated proteins)
- ribosomes
- cytoplasm
- capsule, flagella, pilli
what is the role of the cytoplasmic membrane in prokaryotic cells?
- a lipid bilayer that retains cytoplasm.
- contains proteins (rafts or transmembrane)
- selective
- reaction surface also used for transport of molecules
- energy generation
how is the shape of the plasma membrane in prokaryotic cells determined?
by the type of phospholipids present.
e.g. rods are bent more due to more highly phosphorylated glycoproteins.
how does the nucleoid differ from a nucleus?
no defined location
no histones
no membrane
where does prokaryotic protein synthesis occur in the cell?
near the membrane
what is signifiant to clinicians about prokaryotic protein synthesis?
it is the target of several classes of antibiotic
specifically the tRNA step in the ribosome which is susceptible to interference from drugs
what is the peptidoglycan cell wall made of?
alternating long chain sugars
NAM–NAG
with peptide bridges of 5 amino acids in between
what is the role of the peptidoglycan cell wall?
provide a ‘cage’ around the cell, preventing it from bursting
GRAM POSITIVE
- Thick Multilayered peptidoglycan Layer
- Contains secondary polymer
- strong
- Resistant to osmotic stress
(tends to be slightly more charged)
GRAM NEGATIVE
- Thin peptidoglycan layer
- Outer membrane between extracellular space and peptidoglycan
- Periplasmic space
- Lipopolysaccharides (LPS) (Endotoxin)
- sensitive to osmotic stress
What does penicillin target in both gram neg and gram pos bacterias and why?
The peptidoglycan as human cells do not contain peptidoglycan so it leaves human cells untouched whilst killing bacterial cells
why can drugs like vancomycin target gram positive bacteria but not gram negative?
due to the lack of outer membrane and LPS, large vancomycin molecules can travel down through the peptidoglycan layer and reach the reaction site of the cytoplasmic membrane on gram positive bacteria
what is meant by an endotoxin?
Endotoxins are lipopolysaccharides found in the cell wall of Gram-negative bacteria, which can induce inflammation and fever as an immune response
are flagella and fimbrae present in Gm -ve or Gm +ve bacteria
both
what is the role of fimbrae and flagella?
adherence, (bacterial) sex, motility
what are fimbrae/pilus and flagella?
hair like projections made of protein
what is bacterial sex?
the transfer of DNA between bacteria aka conjugation
what are the 4 requirements for prokaryotic growth?
- food
- temp
- hydrogen ion conc
- osmotic protection
what ‘food’ is required for prokaryotic growth?
*carbon
*oxygen
*hydrogen
*nitrogen source
*inorganic salts (P, S, K, Mg, Ca, Fe)
*trace elements
*vitamins
what is the name given to prokaryotes that grow at body temp?
mesophiles
what are the 4 pashes of the bacterial growth phase?
lag phase
exponential phase
stationary phase
decline phase
