cell communication Flashcards
animal cells communicate by:
same cell
direct contact
local distance
long distance
same cell communication
autocrine
some cancer cells release their own growth hormone
direct contact cell communication
juxtacrine
gap junctions
plasmodesmata
local distance cell communication
paracrine
growth factors, neurotransmitters
long distance cell communication
endocrine
hormones
3 stages of cell signaling
reception
transduction
response
reception
detection of a signal molecule (ligand) coming from outside the cell
transduction
convert signal to a form that can bring about a cellular response
response
cellular response to the signal molecule
binding in reception
between signal molecule (ligand) and receptor
HIGHLY SPECIFIC
2 types of receptors
plasma membrane receptor
intracellular receptors
plasma membrane receptors are
water-soluble ligands
intracellular receptors are
in the cytoplasm, nucleus?
hydrophobic or small ligands
3 steps in reception
ligand binds to receptor protein
protein changes shape
initiates transduction signal
3 types of plasma membrane receptors
g-protein coupled receptors (GPCR)
tyrosine kinase
ligand-gated ion channels
GPCR
7 transmembrane segments in membrane
G protein + GTP activates enzyme, triggers cell response
tyrosine kinase
attaches (P) to tyrosine
activates multiple cellular responses at once
ligand-gated ion channels
signal receptor changes shape
regulates flow of specific ions (Ca2+, Na+)
function of transduction
cascades of molecular interactions relay signals from receptors to target molecules
protein kinase
enzyme that phosphorylates and activates proteins at next level in transduction
what happens when protein kinase phosphorylates
Attached a phosphate group (PO4) to a protein to activate
Only 3 amino acids can be phosphorylated- Threonine (Thr), Serine (Ser), and Tyrosine (Tyr)
purpose of phosphorylation cascade
enhance and amplify signal
second messengers
small, non-protein molecules or ions that can relay signal inside cell
cAMP
cyclic adenosine monophosphate
process involving cAMP
GCPR is converted to adenylyl cyclase (converts ATP to cAMP)
activates protein kinase A
response functions
gene expression: regulates protein synthesis by turning on and off genes in nucleus
regulates activity of proteins in cytoplasm
how is cholera acquired?
drinking contaminated water with human feces
what happens after a person contracts cholera?
bacteria (vibrio cholarae) colonizes lining of small intestine and produces toxin
toxin modifies G-protin involved in regulating salt and water secretion
G-protein stuck in active form
intestinal cells secrete salts, water
how is cholera dangerous?
infected person develops profuse diarrhea and could die from loss of water and salts
apoptosis
cell suicide
dismantled and digested
what is apoptosis triggered by?
capase: triggered by signals that activate cascade of “suicide” proteins
why does apoptosis happen
protect neighboring cells from damage
animal development and maintenance
chemoreception
process by which organisms sense chemicals in their environment
oldest sense is
chemoreception
chemoreceptors
special receptor neurons that receive special information
how does chemoreception different between water and land animals
land: big difference between smell and taste
water: little difference between smell and taste
gustation
sense of taste
taste buds
how taste is sensed in terrestrial vertebraes
what are taste buds made of
chemoreceptor cells that occupy the center of the bud detect the tastant and synapse with a sensory neuron
support cells that form the outer wall of the taste bud and some of the center
tastant
molecule that stimulates a taste
raised papillae
where the taste buds are found on the tongue (epithelium)
how many receptors are used for taste
4-5
5 taste receptors
sour
sweet
salty
bitter
umami
umami
savory-meaty taste associated with MSG
how many chemoreceptors sense smell
about 10,000
taste papillae
little red dots/raised bumps on the front of the tongue
3 other kinds of papillae
foliate
circumvallate
non-gustory filiform papillae
are taste bud receptors spread out or localized
spread out
papila
not the taste bud itself, but many taste buds
sensory nerve
at the base of each taste bud, invades it, branches extensively
reception process
receptor activation –> intracellular signalling (Ca2+ entry) –> neurotransmitter release –> (activation) gustatory neuron
what does the transduction of taste typically involve?
ion channels bound in the membrane
signal transduction of taste
ion channels produce depolarizing potentials when taste chemoreceptor cells interact with tastants
chemoreceptor potentials raise Ca2+ to levels sufficient between the chemosensory cells and afferent sensory neuron
action potential elicited in sensory neuron
higher concentration of chemical =
greater depolarization of the taste cell
transduction of sweet taste
binding of sugar molecule to a receptor cell initiates signal transduction with cAMP and protein kinase A
K+ channels in the membrane close, membrane depolarizes
voltage-gated Ca2+ channels open, Ca2+ diffuses into the receptor cell
synaptic vesicles release neurotransmitters + sends signals to the sensory neuron
what are bacteria
single celled orgnaisms
oldest living organisms
how many genes do bacteria have compared to eukaryotes
few - only have one piece of DNA
how do bacteria make a living
consume nutrients from environment, grow twice their size, then cut themselves down the middle
human cells to bacteria cells comparison
1 trillion human cells and 10 trillion bacterial cells in us
human genes to bacterial genes comparison
humans have 30,000 genes
why would people be considered 1/10% human
we interact with 100 more times bacterial genes than normal genes daily
what do bacteria do for humans thats beneficial
digest food
make vitamins
educate immune system to keep microbes out
what do bacteria do for humans thats harmful
make you sick
what’s the central question that Dr bassler’s lab addresses in terms of how bacteria works
do you want to think about all the good things from bacteria or all the bad things they do?
what are vibrio fisherii
harmless bacteria from the ocean
what is bioluminescence
property that makes bacteria light up
what did Dr bassler notice about bacteria in dilute suspension versus in higher concentrations in terms of their light production
dilute suspension produces no light
higher concentrations produce more light
how do bacteria know when they’re alone or together
by communicating
how do bacteria talk to one another
chemical language
secrete small molecules that detect how many surrounding bacteria there are
where is v fischerii housed
Hawaiian Bobtail squid
how does the symbiosis between the squid and v fischerii work
squid puts up with it because it wants the light
why does the squid benefit from having bioluminescent bacteria in terms of their being an anti predation device
light penetrates the water and the squids becomes visible
bioluminescence allows squid to blend in with reflecting light
what happens to the squids bacteria each morning
squid pumps out 95% of the bacteria
why is the v fischerii communication system important beyond its signaling system? what is this called
bacteria can communicate with one another
called quorum sensing
virulence
bacteria’s ability to harm its host
how does quorum sensing govern virulence? why would bacteria at a low concentration in a human host not launch an attack at their host?
bacteria communicate within your body and attack your immune system. if they don’t have a high enough concentration, they can’t overcome you
how does the structure of the communication molecules allow the bacteria’s signals to be species specific
receptors are the exact shape as the signal molecules, so these conversations are private
what kind of communities do bacteria generally live in? what question does this present about how bacteria communicate
mixtures with hundreds of other species
how do bacteria know what’s around them?
what is meant by that bacteria being multilingual
they have a system that communicates with bacteria of other species
what is meant by bacterial esperanto
all bacteria have a common communicator molecule
what is the practical application of knowing how bacteria communicate with one another
we can stop harmful bacteria from communicating with each other
how can the intra species communication system be used to make species specific antibiotics
there are inhibitors made to be the same shape as the molecule to block the receptor
how can the inter species communication system be used to make broad spectrum antibiotics
the same can be done to block multiple species at once
what have initial animal tests of new antibiotics demonstrated
next gen of antibiotics will help with resistance
what are bassler’s main points from her talk
bacteria talk to each other through chemical responses
how does bacterial communication demonstrate the evolution of multicellularity
they work together to perform virtually impossible tasks
how does bacterial communication demonstrate distinguishing self from other
there are 2 systems that run parallel
how can bacterial communication be used to improve human health
we can prevent bacteria communication with pseudomolecules
why do bacteria produce no light at low cell density and light at high density
when there is a low cell density, the identifier molecules diffuse into the solution
they only activate when there are enough cells that the identifier molecules collide
what happens inside one bacterial cells in terms of its communication with other bacteria
when there are enough molecules outside the cell, the signal receptor tells the cells to turn on the light
intra (bacteria)
communicates with its own species
inter (bacteria)
communicates with all species of bacteria
