2.2 Flashcards
prokaryotic cells
what does a bacterial cell wall being hypertonic mean
water moves into the cell via osmosis as it has higher water potential than outside the cell
why do bacteria cells need a cell wall
prevents swelling & bursting
maintains shape
gives support
protection
what are bacteria walls mostly made of
peptidoglycan
what does a capsule do
protects bacterium from phagocytes
covers cell markers (makes bacteria harder to identify)
may help them survive dry conditions
what are pili and why do bacteria need them
thread - like projections needed to attach to host cell for sexual reproduction
why do pili make bacteria more vunerable to virus infections
can be used as an entry point
what is the structure of a flagellum and how does it move a cell
many stranded helix of protein flagellin
moves via rapid rotations
what are the known as mesosomes potentially used for
artefact from preparing cell for electron micrograph
associated with enzyme activity during separation of DNA & cross walls forming
what may other infoldings in a bacteria cell be used for
photosynthesis
explain plasmids in bacteria
small circles of DNA
reproduce without nucleoid
transferred from one bacterium to another (sexual reproduction)
what is a nucleoid in bacterium
single length of DNA not contained in a membrane
DNA is tangled
what ribosomes do bacteria have
70s (50s + 30s)
smaller
what is gran staining used for
distinguishing gram positive & gram negative bacteria
explain how gram staining effects gram positive bacterium
iodine gets trapped in thick peptidoglycan layer
doesn’t decolour when dehydrated with alcohol doesn’t pick up red safranin counter stain
left purple/blue colour
what are some differences between gram + & gram - bacterial cell walls
gram (+)
thicker peptidoglycan layer
teichonic acid
plasma membrane
gram (-)
thich middle peptidoglycan layer
outer & inner membrane lipopolysaccharides
explain how gram staining effects gram negative bacteria
dehydrated in ethanol dissolves lipopolysaccharide so peptidoglycan exposed iodine washed out therefore take up red safranin counter stain
overall how do antibiotics work
target bacterial cell walls & 70s ribosomes
how do beta - lactam antibiotics work
inhibit formation of peptidoglycan layer
<effect of gram (+)
>effect on gram (-)
how do glycopeptide antibiotics effect bacteria
large polar molecules
<effect on gram (+)
cannot penetrate outer membrane layer of gram (-) bacteria
how do polypeptide antibiotics effect bacteria
interact with phospholipids of the outer membrane
<effect on gram (-)
X effect on gram (+)
how do other antibiotics effect both bacteria equally
target processes such as protein synthesis carried out by 70s ribosomes
how can you classify bacteria
- shape
-respiratory requirements - gram +/-
state the 4 shapes of bacteria
spherical (cocci)
rod-shaped (bacillic)
twisted (spirilla)
comma-shaped (vibrious)
explain the 3 respiratory requirements of bacteria
obligate aerobes - need oxygen
facultative -anaerobes fine with/without oxygen
obligate anaerobes - cannot have oxygen
roughly how big are viruses
0.02micrometers - 0.3 micrometers
what parts do all viruses have
genetic material
capsid
receptors
what is a capsid made of
repeating protein units known as capsomeres
what is the role of VAPs (virus attachment particles)
attach viruses to their host cell
give examples of DNA viruses
small pox
lambda phage
what are bacteriophages
viruses which infect bacteria
are DNA viruses or RNA viruses more likely to mutate
RNA
more steps in replication
what type of virus is the immunodeficiency virus
RNA retrovirus
name a positive ssRNA virus
tobacco mosaic virus
name a negative ssRNA virus
ebola
what viruses always have a protein capsid and lipid envelop
retroviruses
why are viruses not classed as living
they cannot reproduce on their own
what happens when a virus is taken in via endocytosis
host cell then digests capsid releasing genetic material
what is the most common way that viruses infect cells
viral envelop fuses with host cell surface releasing viral genetic material into cell
how do viruses often get into plant cells
vectors
insects pierce cell wall
what does non-virulent & virulent mean
non virulent- not disease causing
virulent - disease causing
what occurs in the lytic pathway
viral genetic material is replicated independently of the host DNA
what is a provirus and when is it formed
the DNA thats inserted into the host cell during the lysogenic cycle
When can viruses in the lysogenic state be activated
- host is damaged
- repressor/ protein decreases
how do positive ssRNA viruses replicate
genetic material enters cell
single sense stand used directly as mRNA
translated by ribosomes into viral proteins
how do negative ssRNA viruses reproduce
genetic material enters cell
circus imports RNA replicase
antisense strand transcribed to sense stand by RNA replicate
free bases act as mRNA
transcribed by ribosomes into viral proteins
what enzymes are needed in reproduction of retro viruses
reverse transcriptase
integrase
how do viral particles leave the host cell in the reproduction of retroviruses
exocytosis
how do viruses cause symptoms of disease
lysis of host cell release their own lysosomes
digest themselves produce toxins
why are virus infections often specific to particular tissues
due to the presence of absence of cell markers on host cells viruses can only bind to particular markers
who does foot & mouth disease effect
coven-hoofed animals
how is foot & mouth disease spread
body secretions (milk)
food & water
contact with diseased animals
how is ebola spread
bodily fluids and blood
direct contact
how do antiviral treatments work
target receptors
target enzyme for translation or replication of DNA/RNA
inhibit protease enzyme
what do antiviral treatments do
reduce the time a persons sick
delay development of symptoms
