Exam 2 Flashcards
Tetracycline
Inhibits protein synthesis
Block tRNA binding site
Chloramphenicol
Inhibits protein synthesis
Block peptide formation
Gramicidin
Disrupts cytoplasmic membrane of gram +
Skin only
Lincomycin
Inhibits protein synthesis
Prevent ribosome movement, stop translation
Polymyxin
Disrupts cytoplasmic membrane of gram -
Toxic: kidney and nerve damage
Antibiotic of last resort
Amphotericin B
Disrupt cytoplasmic membrane of fungi
Attaches to ergosterol
Nystatin
Disrupt cytoplasmic membrane of fungi
Attaches to ergosterol
Sulfonide
Targets metabolism
Structurally mimic PABA
Interacts with and then shuts down an enzyme needed for folic acid biosynthesis.
Consequences of broad spectrum
Secondary infection
gene
unit of inheritance that determines traits that are passed on
allele
variation of a gene
genome
collection of all genetic material in a microbe is here
Transcription and Translation path
Replication / Genes (DNA) –> transcription –> RNA message –> translation –> protein / products
enzyme for replication
DNA polymerase
replication initiation
For a cell to divide it must first replicate it’s DNA. This process is initiated at the origins of the DNA which are targeted by the initiator protein
Initiator proteins tend to use A-T rich sequences
pre-replication complex “unzips” the DNA
Chargaff’s rule
DNA from any cell of all organisms should have a 1:1 ratio (base Pair Rule)
DNA is read in the (___) direction, but synthesized in the (___) direction
3 to 5
5 to 3
DNA replication in cellular life requires a free what? (___) is used to synthesize a short RNA primer with a free (___) which is elongated by DNA polymerase
3’ hydroxyl group
Primase
3’ OH group
The replication fork
After elongation helicases break the H bonds hold both strands together in DNA. The forks become the leading and lagging strand
How is the lagging strand different from the leading strand?
The lagging strand is synthesized in the opposite direction
Leading strand
Polymerase (sigma) reads the leading strand template and adds complementary nucelotides to the nascent (new) leading strand
Lagging strand
Synthesis in opposite direction to replication fork Must be synthesized in short , separated segments Primase reads the template DNA and initiates synthesis of a short, complementary RNA primer DNA polymerase (delta) extends the primed segments. RNA primers are removed and replaced with DNA
RNA polymerase: the (___) is responsible for assembly of RNA while sigma finds (___) on the DNA strands where RNA polyermase can bind
core
promoters
DNA replication ends at the (___) region
telomere
Transcription
RNA polymerase unwinds a small piece of DNA into ss, sigma falls off
RNA nucleotides float in and base pair
RNA polymerase polymerizes RNA
Translation initiation
protein synthesis
1) ribosome assembles on the mRNA at the shine-dalgarno sequence
2) activated tRNAs arrive at the ribosome
Translation elongation
3) a peptide bond is formed between the two amino acids
4) ribosome slides three nucleotides down the mRNA
5) New activated tRNA arrives and ribosome forms another peptide bond (repeat cycle)
6) protein is synthesized from N terminus to C terminus as cycle repeats
Translation termination
stop codon signals the termination of protein synthesis
the protein is released, the ribosome disassembles
Where is the start site of translation?
6-9 bases in the 3’ direction of the Shine-dalgarno sequence at a AUG codon
What is a codon?
a series of three nucelotides
they specify a particular amino acid by calling over the right tRNA
set the frame for determining future codons
Codons are on the _RNA while anticodons are on the _RNA
m
t
Start codon = ___
Stop = ___
AUG
UAG, UUG, UAA
Direct transfer of DNA from one cell to another
Conjugation
Transfer of genetic material between bacteria via a virus
transduction
Antiseptics vs disinfectants
Living tissue instead of non-living surface
Alcohol and iodine are antiseptics (iodine evaporates faster)
Sanitize vs sterilize
remove some instead of removing all
Aseptic is the result of sterilization
cide and cidal
kills (cut) and has the power to kill
Heat
Dry:
Moist:
Denatures proteins, disrupts membranes and viral envelopes, melts DNA to ss
Dry: baking, incineration (direct flame)
Moist: boiling, autoclave, pasteurize, ultra-high temp
Autoclaving
steam under pressure, 121C for 10 minutes kills all
Pasteurization
63C for 30 or 71C for seconds
Ultra-high temperature sterilization
134C for 1 second, affects taste
Thermal death point
Thermal Death Time
Thermal death point: lowest temp that kills all micro-organizms in a liquid in 10 minutes
Thermal Death Time: time to sterilize a volume of liquid at a set temp.
Refrigerator
0-7C
slows growth
membranes shatter
proteins become inflexible and denature
Freezing
negative temp C
halts growth
water unavailable
ice crystals puncture cells
Dessication
removes water which proteins need
chromosomes fragment (lethal)
principle behind jellies (sugar), brines (salt), and curing (salt)
Oxygen radicals
H2O2, NaOCl, O3 all make them and they react with and damage any macromolecule they contact
Radiation
UV light can cause mutation
Ionizing radiation: (x rays, gamma rays) creates water radicals
OH- rips protons from DNA to form water
Chemicals:
1) alcohols and halogens
2) heavy metals
3) detergents and phenolics
4) specific targets
protein denaturants
poisons (inactivate proteins)
membrane disruptors
antibiotics
Alexander Flemming
penicillin
Gerhard Domagk
sulfonamides to kill bacteria
mechanisms of antimicrobial actions
inhibition of cell wall synthesis, protein synth, pathogen attachment, DNA / RNA synth, general metabolic pathway or disruption of membrane
Inhibition of cell wall synthesis
beta-lactam: antibiotics that prevent the NAM in petidoglycan from forming cross linkers (penicillin and methicillin)
Bacitracin and vancomycin
No effect on existing peptidoglycan or microbes without it
Inhibition of protein synthesis
Selectively targets the 70s ribosomes translation
Dangerous because our mitochondria also have these
Streptomycin
Inhibition of protein synthesis
changes shape of 70s ribosomes
(Fluoro)quinolones
target replication and transcription
act against replication enzymes specific to bacteria
Antibiotic resistance strategies
Exclusion (prevent entry)
Destroy the antibiotic
Modify it
Immunity by modifying the target
Nosocomial infection
hospital acquired
