RE revise Flashcards
what is needed before replication can occur
initiator protein must bind to the origin of replication
what does DNA topoisomerase do
aids unwinding process
what does DNA helicase do
breaks hydrogen bonds between bases
form two single strand template strands
where is the RNA primer needed
added to 3’ end
what does DNA primase do
synthesises short RNA primer (5-10 nucleotide bases)
attaches primer to 3’ end of template
what does DNA polymerase do
reads template strand 3’ to 5’
causes nucleotide addition to primer
cataylses the phosphodiester bond forming between 3’ carbon of last nucleotide and 5’ phosphate of incoming nucleotide
what does DNA ligase do
joins okazaki fragments to form DNA strand
translocation in eukaryotes
scans 5’ UTR
mRNA unwound and more proteins added/bind
mRNA attaches to complex with poly (A) tail at end
tRNA brings methionine, binds to form a large complex
what is rho-dependent
rho interacts with elongating RNA transcripts
disrupts interaction causing RNA polymerase to ‘fall off’
what is rho-independent
RNA forms hairpin loop due to inverted repeats in DNA
hairpin loop stops RNA polymerase transcribing
followed by uracil poly tail - only weakly bound to poly A sequence so RNA falls off as no strong connection between DNA and RNA
eukaryotes transcription termination
AAUAA cleavage signal
signals RNA ending
specific endonuclease cleaves off poly (A) tail added
eukaryotes translation termination
termination codons at end of protein-coding sequence
tRNAs don’t have complementary anticodon
release factors bind to ribosome
release mRNA from ribosome-complex falls apart
prokaryote initiation
ribosome dissociation
IF2 and GTP complex with formyl methionine tRNA
tRNA brought to mRNA, complementary to AUG codon on mRNA
form 30S initiation complex
IF3 lost
GTP hydrolysed to GDP (+Pi) produces energy
energy displaces IF1 and IF2 so 50S can re-associate
prokaryote elongation
EF-Tu binds with GTP to next complementary tRNA in mRNA sequence
tRNA brought to A site, binds = release EF-Tu and GTP
peptide bond forms between amino acid in P site and A site
catalysed by peptidyl transferase
GTP hydrolysed = energy for ribosome to be shifted three nucleotides right till reach stop codon
what is the cell pathway in eukaryotes
contractile microfilaments of cytoskeleton - lines of tension in cell
energy transmitted through these lines, lets cell move across
what is the cell pathway in extracellular matrix
extracellular matrix has fibronectin fibres
each cell orientated to position of fibronectin fibres
follow fibronectin trails
how do adheren junctions form
cadherin proteins cross intracellular space link to catenins
catenins linked to actin filaments
actin filaments anchored to cytoskeleton
how do desmosomes form
cadherins cross intracellular, other proteins link cadherins to intermediate filaments
attached to skeletal proteins inside cell
anchored to intermediate filaments of cytoskeleton
how do tight junctions form
tightly packed row of protein ridges linking adjacent cells
ensure adjacent cell membranes held together
how is a lateral root formed
outer tissue disformation and cell separation
signals outside cells to release cell wall modifying enzymes
allow cells around to stretch move and disengage with each other - can grow through
lateral root contains all same material as primary
what is sclerenchyma and its function
provide structure and support to plant tissue
cell walls are thick lignified secondary walls made of cellulose and hemicellulose - often die when age
what is special about phloem cell wall
perforated using sieve plates to allow compounds to travel through
what is the sclereid and its function
keeps plant together
gives structure and strength without preventing it moving in water
what is the collenchyma and its function
elongated cells with thick cell walls
provide structure and support
cellulose and pectin are irregularly thickened at corners
what are hydrophytes
important for aquatic plants
stomata only on top of leaf
epidermal layer very little strengthening in stems = not rigid
AERENCHYMA form air channels for gas exchange
what is the plasma membrane function
coordinates synthesis and assembly of cellulose microfibril
control substances in/out cell via transmembrane protein
relay hormonal and environmental signalling factors
what is the function of the perioxisome
detoxes cell
help cell survive in toxic environment
hydrogen peroxide is a metabolic waste product, toxic to cell
perioxisome converts it to water
golgi body function
provides a network of vesicles for secretory purposes
sorts - proteins know where need to go, packages for transport
modifies products from rough ER
what is the vacuole function
regulate turgidity by regulating water in cell
what is a vacuole
membrane bound organelle filled with cell sap
often acidic pH, many have toxic/bitter compounds - stop being eaten
what is lytic infection
host cells destroyed - virus particles released
normally clears in couple days - immunity
some hosts not immune = epidemic
what is latent infection
lack of gene expression, normally in sensory and autonomic ganglia - immunocompromised
lasts lifetime of host
UV can reactivate - re-enter lytic cycle
what is persistant/chronic infection
virus does not cause cell death
slow virus release
if not good immunity can last long time
what is a germ cell
cell containing half the number of chromosomes of a somatic cell and is able to unite with one from the opposite sex to form a new individual - a gamete
what is heterogametic
X- Y- hemizygous for genes (only has one copy of genes)
what is polyploidy
condition in which cell/organism has more than two sets of chromosomes
what is the paracellular route
materials cross through junctions between cells where there is a gap
what do motor proteins do
change the position of things in the cell
what is endocytosis
a living cell takes up matter via an invagination in the cell membrane
what is exocytosis
vacuole contents released to exterior as vacuole membrane fuses to cell membrane
what is pinocytosis
liquid ingested into cell due to small vesicles budding off cell membrane
what is saltatory conduction
transmit change by reversing local electric field that passes along nerve axon - active signal. Regenerated along axon
intracellular inclusions
contain insoluble chemical deposits
used as storage organs
bounded by non-unit membrane
what is the effect of a bacterial phospholipid bilayer
hydrophobic core - barrier to most water soluble molecules protein permeases (membrane transport protein) allow selective transport of molecules in
what are the benefits of cytoskeleton on plant cell
vesicles from ER and golgi travel along monorails it provides
growth in particular direction
involved in positioning organelles
what is a heterotroph
relies on carbon from complex compounds
what is a phototroph
photosynthetic microbes
what is binary fission
transfer of genetic material before septum formation or will not be viable cells
what is a bacterial endospore
dormant structure
can permit for long time
dehydrated, no biochemical reactions occur
germination and outgrowth lead to new vegetative cell
what were Kochs postulates
gene found associated with pathogen
mutation attenuates virulence of pathogen
transfer of gene can give other organisms disease
what are exotoxins
extracellular diffusible toxins
normally proteins secreted during exponential growth
how does an enveloped virus enter/exit cell without destruction
envelope pinches off bit of plasma membrane
envelope glycoprotein on outside of capsomere fuses with outside of cell
release nuclear capsid into cytosol
what is the capsid function
encapsulates nucleic acid - no harm
interact with cell organelles
genome delivery - binds to receptor using spikes
what is a transposon
small DNA pieces = replicate and move round in genome insert themselves
where can clostridium botulinum be found
associated with meat or canned foods not reheated before eating
heat sensitive but germinates in cooled food
where can bacillus cereus be found
spores are heat resistant and germinate in cooled food after cooking
cereals and rice survives in reheated foods
where can clostridium perfringens be found
natural part of animal gut microflora
spore found in faeces
associated with cooked meat products
where can campylobacter be found
mainly from poultry or other raw meat
natural habitat is bird intestine
where can listeria be found
normal habitat is mammal intestine, soil and plants
can grow in refrigeration temperatures
many sources e.g. dairy, salad, cold meat
what is post transcriptional gene silencing
Gene silencing small interfering RNA cause mRNA degrade, can’t be translated to proteins
what must happen for eukaryote transcription initiation to occur
several transcription factors bind to core promoter TATA box - must be specific combination of TFs for RNA polymerase to bind
