2.2 Flashcards
(36 cards)
what does the bacteria cell wall do
hypertonic contents so water moves in by osmosis
prevents swelling and bursting
maintains the shape of the bacterium
support and protection to contents of cell
some have slime capsule protects from phagocytis by white blood cells
peptidoglycan
all cell walls consist of a layer
made up of many parallel polysaccharide chains with short peptite cross linkages making net like structure
pili
some bacteria have one to several hundred protein projections
used for attachment to host cell and sexual reproduction
more vunrable to bacteriaphage (virus)
cell surface membrane
similar in both pro and eu but pro have no mitochondria so membrane is site of some respiratory enzymes
some have mesomes
plasmid
small circles of dna
codes for a particular aspect of the bacterial phenotype
can reproduce independently of the nucleoid
can be transfered by pili
nucleoid
genetic material conists of single length of dna often circular not contained in the membrane bound nucleus found in the nucleoid
gram postive
thick later of peptidoglycan
staining trapped in layer so remains purple
has teicholic acid
no outer membrane
no lipids
gram negative
thin later of peptidoglycan
staining goes pink
no teichonic acid
outer membrane
has lipids
antibiotics
some inhibit formation of peptioglycan therfor affective against positive
some can penetrate thin negative layer but cannot get through positive
shapes of bacteria
spherical - cocci
rod - bacilli
twisted - spirilla
comma - vibrios
obligate aerobes
need oxygen for respiration
faculitative aerobes
use if available but can manage without
obligate anerobes
can only respire when no oxygen
virus structure
some have envelope which makes easy to pass but more vunrable to substances entering
capsid (protein coat) is made of repeating units (capsomeres)
dna viruses
genetic material is dna
acts as template for both new dna and mrna needed for viral proteins
e.g
- small pocks
-lamda phage
rna viruses
70% have rna
much more likely to mutate
positive sense
can be translated at ribosomes
-tobacco mosaic
-polio
-hepatitis c
negative sense
- ebola
-measles
must be translated before translated at the ribosomes
lytic pathway
virus attaches to host cell
inserts genetic material
viral proteins made
virus multiplys by DNA replication
cells lyses viruses released
virulent (disease causing)
viral entering cell
endocytosis then host digests capsid releasing genetic material
viral envelope fuses with the host cell surface releasing rest of the virus
vector
lysogenic
non virulent
they insert their dna into the host dna so it is replicated everytime the host replicates
host is a provirus
virus is latent
however if the host is damaged it can enter the lytic pathway
rna retrovirus
protein capsid and lipid envelope
single strand rna directs enzyme reverse transcriptase this goes on to make dna corresponding to the viral genome
incorporated into the host cell dna and used as template
-hiv
positive rna virus replication
makes rna polymerase which replicates the viral rna
negative rna replication
antisense strand must be translated into sense strand by rna replicase
rna retrovirus replication
translate the viral rna into dna by reverse transcriptase then passes into the nucleus of host cell and inserted into dna new viral material is syntehsised and the new particles leave by exocytosis and the host cell continues function and virus making
how to stop virus
target enzymes help translate or replicate the viral dna or rna
inhibit the enzymes that enable new virus particles to bud
