MicroBio Flashcards
what is an obligate intracellular parasite?
this is the definition of a virus
obligate - relies on host
intracellular - must enter the hosts cells
true or false, some viruses can make ATP
false - viruses cannot perform any sort of chemical reactions –> need host machinery.
some viruses may carry host ATP within their capsids
t or f, a virus can contain both DNA and RNA in its genome
false - viruses only contain one kind of nucleic acid in their genome 99% of the time
what is a bacteriophage
a virus that infects bacteria
explain the viral genome size. what is the consequence of this?
the genome size is very small as its packed tightly into the viral capsid which is non-pliable. one consequence of tis is that the viral genome is polycistronic (more than one protein per gene) –> multiple reading frames
what is helical vs polyhedral? what is the head, tail fibres, base plate, and sheath?
helical - rod like capsid
polyhedral - multiple-sided capsid
head - capsid which holds nucleic acid
tail fibres - bind the cell surface and press the base plate onto it
sheath - uses stored ATP to contract and inject nucleic acid into the cell
why do bacteriophages inject their genomes while animal viruses do not (in general)?
bacteria have cell walls which must be penetrated.
animal cells don’t and thus, he virus can be internalized naturally.
what is budding and what is an envelope?
some viruses are enveloped in which they acquired a membrane around themselves from the previous host cell. the process of a virus moving through a PM and taking some membrane with it is called budding.
t or f, all plant viruses and bacteriophages are naked viruses (non-enveloped).
true - since enveloped viruses do not inject their genomes which must be done to penetrate the cell wall
what is
- attachment / adhesion
- penetration / eclipse
for bacteriophages
- attachment of virus to the cell based on specific proteins in the cells capsid (or envelope for animal viruses)
- eclipse is the actual entrance of the genome via injection
the lytic cycle:
once infected, the virus is immediately transcribed / translated. what is the product of an important early gene
hydrolase is created - this degrades host DNA.
the lytic cycle: why is hydrolase important?
hydrolase provides free dNTP’s that can be used for viral DNA replication
the lytic cycle: once DNA replication has occurred + translation of Capsid proteins (etc.) what is an important late gene produced and what does it do?
lysozyme is produced which is an enzyme that degrades cell walls –> this breaks the bacterial cell wall and causes it to lyse (lytic cycle)
if a virus was cultured in cells with radio labeled cysteine and phosphate, which of these two molecules will be found in the next cell the virus infects.
- cysteine will be incorporated into the initial capsid proteins
- phosphate will be incorporated into the nucleic acid
the next cell will be injected with phosphate-rich nucleic acid but the capsid remains on the outside.
The lysogenic cycle of phages: the lytic cycle is problematic since it kills of all of its host cells. what is a prophage and a lysogen?
prophage - this is when the viral genome integrates with the host genome
lysogen - a bacterium with viral genome integrated in its own genome
The lysogenic cycle of phages: t or f, once in the host DNA, the viral segment gets replicated and transcribed over and over again.
false
- it does repeatedly get replicated as the bacterium performs replication
- it is dormant in terms of Tx. this is allowed since a repressor protein sits on its promoter site
The lysogenic cycle of phages: what is excision?
when the prophage leaves the host genome. now it can enter the lytic cycle
What is transduction?
when the prophage is excised from the host genome, it may inaccurately do this and bring along some host DNA with it. Sometimes this DNA carries a full trait / gene and thus introduces a new phenotype for the next bacteria that is infected
what receptor does gp120 of HIV bind?
CD4 of T cells
t or f, some viruses carry with them and use host proteins.
true –> e.g. when budding occurs, the virus brings with it all embedded proteins
what is uncoating?
when an animal virus enters a cell via endocytosis, the capsid must be removed to expose the genome.
what is an animal viruses productive cycle?
animal viruses exhibit lytic, lysogenic, and productive cycles –> this is the lytic cycle except it does not kill the cell at the end since it buds via exocytosis.
what is a provirus?
a prophage but for animal viruses
explain RNA (+) viruses in terms of
- what there genome is
- what they must bring / encode
- how their Tx / Tl / replication occurs
- there genome is a + sense strand of mRNA meaning they can be directly translated by host cell enzymes.
- Translation can occur immediately, but no host cell can Tx or replicate RNA –> therefore, RNA (+) viruses must encode RNA-dependent RNA polymerase.
replication: to make more + strands of the RNA genome, the RNA polymerase first makes a (-) strand and then uses this new template to create many (+) strands.
why does it mean when we say a genome is infective?
it is an RNA (+) strand since it can be directly translated
explain RNA (-) viruses in terms of
- what there genome is
- what they must bring / encode
- how their Tx / Tl / replication occurs
- this is an antisense RNA strand meaning it cannot be translated.
- since it cannot be translated, RNA (-) viruses must BRING RNA-dependent RNA polymerase. This transcribes a (+) mRNA which can a. be translated and b. be used as a template for RNA replication.
note: it also encodes for RNA-dependent RNA pol
explain retroviruses in terms of
- what there genome is
- what they must bring / encode
- how their Tx / Tl / replication occurs
- retroviruses are simply RNA (+) viruses which integrate into the host DNA thus becoming prophages / lysogenic. since its RNA (+) it can first be translated.
- it encodes reverse transcriptase (RNA-dependent DNA polymerase). this creates DNA from RNA. this DNA is then incorporated into the hosts genome
what kind of genome does these have?
common cold
HIV
measles
common cold - RNA (+) genome
HIV - retrovirus
measles - RNA (-) genome
explain a ds-DNA virus in terms of
- what there genome is
- what they must bring / encode
- how their Tx / Tl / replication occurs
- its made up of ds DNA. This means it can use host cell enzymes for Tx and replication.
- these viruses typically encode enzymes for dNTP synthesis and DNA replication –> rather then waiting for the host cell to do it.
what is a prion?
a misfolded protein which acts as a template to cause more proteins of its kind to also misfold
what are transmissible spongiform encephalopathies? give examples.
TSE’s are caused by prions
from ingestion
mad cow disease
kuru
from inheritance
CJD
FFI
what are viroids?
these are single stranded pieces of circular RNA. Many of the bases undergo self-complementary pairing.
these don’t code for genes other then genes which may cause its replication (may code for RNA-dependent RNA polymerase)
what are the three tenets of cell theory?
- all life is made up of 1 or more cells + their products
- the cell is the monomer of the organism
- all cells come from pre-existing living cells
what are the domains? what are the kingdoms of Eukarya?
Bacteria and Archaea (domains) which are prokaryotes
Eukarya (domain) which are eukaryotes
- plant, animal, and fungi (kingdoms)
what is the major difference between eukaryotes and prokaryotes?
prokaryotes do not have membrane-bound organelles nor a nucleus.
what is a protist?
a single cell eukaryote
what is a plasmid?
this is an extra-chromosomal genetic element which can control its own replication and transcription –> often provides a certain trait
what is
cocci
bacilli
spirilla
These are bacterial shapes
cocci - round
bacilli - rod-like
spirilla - spiral shape
what is the difference between gram negative and gram positive bacteria?
gram + –> these are stained strongly (purple) and contain a fat peptidoglycan layer above their membrane
gram (-) - stained weakly (pink) and contain a thin peptidoglycan layer and an outer layer above its membrane.
where id D-alanine found?
in the peptidoglycan layer of bacteria. Note that D-AA’s are not found in animals
t or f, gram (+) bacteria are more vulnerable to lysozyme and penicillin.
true since it lacks the outer membrane protection
what is an endotoxin, what is an exotoxin?
endotoxin –> a molecule that exists on the surface of a bacteria which causes an immune rxn. e.g. LPS on gram (-) bacteria
exotoxin - a toxic molecule that is secreted by either kind of bacteria
what is a capsule?
this is a polysaccharide glue secreted by bacteria to increase its defence and adherence to things
what is the flagella and explain its structure
allows for motility
- basal structure -> includes a rod that spins and rings around it
- hook - connects the rod to the filament
- filament - causes motion
t or f, prokaryotic and eukaryotic flagella are the same
false
eukaryotic exhibits a 9 + 2 microtubule arrangement discussed later
what are mesophiles, thermophiles, and psychrophiles?
mesophiles - bacteria that like normal temperatures
thermophiles - like hot
psychrophiles - like cold
explain chemoautotroph chemoheterotroph photoautotroph photoheterotroph
chemoautotroph
chemoheterotroph –> us, we get energy from chemicals and we store in in food products that we take from other species
photoautotroph
photoheterotroph
the first part explains where we get our energy
the second explains how we store it
what is minimal media? what is a lawn? what is a plaque?
minimal media = agar + glucose (or one single growth substance)
lawn = regions of dense bacterial growth –> many colonies
plaque –> area in between the lawn which indicates bacterial lysis from viral infection
what is an auxotroph?
a bacteria which cannot live on minimal media since it cannot synthesize a certain substance
- e.g. arginine = Arg-
explain obligate aerobes facultative anaerobes tolerant anaerobes obligate anaerobes
obligate aerobes - need oxygen
facultative anaerobes - use oxygen when present but do not need it
tolerant anaerobes - oxygen has no effect on it
obligate anaerobes - oxygen poisons it
what is anaerobic respiration?
this is not fermentation - anaerobic glucose metabolism
respiration - implies aerobic glucose metabolism
anaerobic respiration –> glucose metabolism where the final electron acceptor is NOT oxygen
e.g. reducing CO2 to CH4
what is binary fission?
the process of a bacterium building up enough resources and replicating its DNA once followed by it simply splitting in half (this is the actual fission)
lag, log, stationary, death?
these are the phases of a bacteria’s life
lag - not dividing but preparing for division
log - exponential growth
stationary - the media is running out of nutrients and building up toxic waste
death
if a bacteria in a log phase moves to a fresh culture, will it show a lag phase?
no. all supplies have been acquired and thus will continue to divide in the log phase.
what is an endospore? what bacteria make it?
endospores are hibernation pockets in which gram positive bacteria place their important supplies into to survive stressful times
what is germination?
the process of an endospore reactivating
what is transformation?
when a bacteria picks up a random floating piece of DNA and incorporates it into itself
what is conjugation?
when a bacteria contains the fertility factor ( a plasmid which codes for a sex pilus), it can transcribe this factor and form a conjugation bridge with another bacterium. it then can replicate this factor and pass it through the conjugation bridge
can F+ transmit to F+?
no, only F+ to F- or Hfr to F-
what is an Hfr cell?
in this case, the fertility factor plasmid has integrated into the host chromosome( Now called Hfr = high frequency of recombination) . Now when the fertility factor is replicated to be passed along the conjugation bridge, some host DNA may be replicated with it. This is how recombination occurs in bacteria –> the copied gene recombines with the host cell DNA of the F- receiving bacterium.
true or false, viroids have capsids
false
t or f, bacteria cannot increase their genetic diversity (aside from mutation).
false, binary fission does not increase diversity but conjugation can increase diversity.
t or f, arachaea have a peptidoglycan layer
false
t or f, archaea have some genetic similarity to eukaryotes
true, they contain introns whereas bacteria do not.
for this reason archaea seem to be in the middle between prokaryotes and eukaryotes
