Cell Signaling Flashcards
Signal Transduction Pathway
a series of steps in which cells send signals and create cellular responses with the use of receptors and ligands
Transduced
when a mating signal is changed because it is received by the receiving cell and the signal causes a cellular response
If signals are not reduced can reactions happen
no –> there is no cellular response
Paracrine signaling
type of signal where a signal is sent out to the area surrounding it and the only cells that can pick up on it are the ones with the proper receptors
How many types of local signaling are there and what are they
2: paracrine signaling + synaptic signaling
Synaptic signaling
sends chemical signal directly to a specific cell (through a gap called a synapse)
what are the only types of cells that use synaptic signaling
neurons
Local signaling
signaling cells that are around you
Long distance signaling aka
hormonal signaling
hormonal signaling
signal from endocrine cell gets sent to the blood and it goes throughout the body and then goes to thee target cell (specific cell with specific receptor)
endocrine cell
hormones
How many types of hormonal signaling and what are they
2: animals and plants
Animals hormonal signaling
through the circulatory system
What are some examples of things that come out of synaptic signaling
dopamine
What are some examples of things that are caused by paracrine signaling
growth factors (like HEY BITCHES DO MITOSIS)
endocrine signaling of plants (way 1)
plants obvi don’t have hormones so plant factors send signals through the xylem and the phloem and these go to other cells (plasmodesmata)
endocrine signaling of plants (way 2)
can send signals through the air with gas
Direct contact signaling for animals
gap junctions, tight junctions, desmosomes or sending signals through the cytoskeleton
Direct contact signaling for plants
cytoplasmic channels (plasmodesmata)chemicals directly flow from one cell to the next
Ligand
small molecules that bond to large receptors
Examples of ligands
chemical signals
What are the three steps of cell Signaling
reception Transduction response
Reception
cells receive signals (usually on the membrane –> proteins) can be on the inside of the cell
Transduction
proteins (relay molecules) change their shape when chemicals bind to the receptor and this happens in steps
Response
signal is interpreted and smth happens in the cell
What are some examples of things that can happen in response
transcription factor
activator
inhibitor
membrane receptor proteins
in membrane bc hard to go through the membrane
G-protein linked receptors
cell surface receptors that are water soluble signaling molecules that transfer signals from the ECM to the inside of the cell
How do g protein linked receptors work
so the signaling (ligand) gets added to the receptor that’s on the cell membrane
this makes the g-protein that’s js hanging there get activated by turning the GDP on it into GTP
this then goes to the enzyme thats chilling there and the g protein activates it and it does some cellular response type shiiiii
Chemical signals usually come in the form of what
ligand
Tyrosine Kinase receptors
plasma membrane receptors that induce cell responses
What happens to the gcpr when the ligand binds to it
it changes shape!
What happens to the enzyme in the gcpr pathway when the g protein binds to it
it changes shape when it becomes active!
What happens in the gcpr pathway when the enyzyme catalyzes a response or smth
the g protein hydrolyzes itself: GTP –> GDP + P
When the GTP turns back into GDP what does the enzyme do
it moves away from the g protein
G protein functions
yeast mating factor
many hormones such as epinephrine
embryonic development
vision and smell
Dephosphorylation
inactivating protein kinase by removing phosphate groups
Tyrosine-Kinase Receptor
plasma membrane receptors that induce enzymatic activity and can trigger MULTIPLE transduction pathways
How many molecules is a tyrosine Kinase receptor made of and what are they
2 monomers (amino acids)
How do tyrosine Kinase receptors work
the 2 proteins are turned on by ligands (signal molecules) and they come together to form a dimer
now since its active the RTKS phosphorylate the tyrosines and the RTKS are active and they can bind to relay proteins which can cause cellular responses
Kinase
enzyme that catalyzes the transfer of phosphate groups
Tyrosine
amino acids that are on the substrates (the RTKS)
Do the RTKs phosphorylate their own tyrosines
they phosphorylate each other
Tyrosine-Kinase uses
growth factors
many hormones such a as insulin
Ion Channel Receptors
type of membrane receptors that have a region that acts as a gate which opens and closes to lets special ions such as Na+ or Ca2+ in
How do ion Channel Receptors work
a ligand binds to theproiten and opens the gate and lets the ion go through
Ion channel receptor uses
neurotransmitters
Intracellular receptors
found in the cytoplasm or nucleus of target cell and they have reactions like turning genes on or off
How do intracellular receptors work
signal molecules go through the membrane and the nuclear membrane without proteins because they are small and hydrophobic and they bind wherever on DNA to make a mRNA copy (polymerase does this) which then makes a specific protein which makes another pathway and cellular responses blah blah blah blah
Transcription Factor
proteins that control which genes are turned on (can control multiple genes)
Why do signal transduction pathways have multiple steps
bc it allows there to be easy regulated reactions
What causes the changing of the shape of the signal at different steps
phosphorylation
Most relay molecules in the pathway are
protein kinases
How does a phosphorylation cascade work
so first there’s the receptor and the ligand binds to it and then the active receptor will activate a relay molecule
that relay molecule is gonna dephosphorylate an in active protein kinase to make the next one an active protein kinase
then that protein kinase dephosphorylate a diff inactive protein to make another one active and you repeat until you make an inactive protein an active protein
Why is dephosphorylation useful
because it is useful bc it always allows thing to be off and on when needed
how are things getting from inactive to active
they get an added phosphate
Secondary messengers
the first thing in the pathway
Examples of secondary messengers
signal molecules
Secondary messengers are (what type of molecule)
nonproteins that can go through the membrane by diffusion
Relay molecules
proteins that send signals to a spot and its usually not a protein
Protein kinase
molecule that adds phosphate to another molecule
phorphorylation cascade
each protein acts as a kinase to each other
Most common secondary messenger
cyclic AMP
cAMP stands for
cyclic adenosine mono phosphate
Water Potential
the measure of potential energy in the water when the temp and pressure are constant
When does water Potential happen
movement of free water molecules
Water Potential symbol
ψ
Osmotic Potential
the potential of water molecules to move from a hypotonic solution to a hypertonic solution across a semi-permeable membrane via osmosis
What causes osmotic Potential
dissolved solutes
Osmotic Potential symbol
ψs
Osmotic potential aka
soltute potential
Pressure Potential
the pressure water applies on neighboring solutions due to physical forces
Pressure Potential symbol
ψp
When is ψp positive
when the physical pressure is greater than atmospheric pressurre
When is ψp negative
when the physical pressure is less than atmospheric pressure
When is the i in the solute potential equation negative
when there are solutes in the solution
Common secondary messengers
nitric oxide, cAMP, DAG, IP3, calcium
Pathway of cAMP
- GPCR pathway
- the enzyme is adenyl cyclase
the adenyl cyclase activates the cAMP with ATP - the cAMP activates the protein kinase which activates a cellular responses
Where does the ATP come from in the cAMP pathway
from the energy from the GTP with g protein bindind to it
what pathways can calcium be used as a secondary messenger
GPCR and RTK pathways
why can calcium be used as a secondary messenger
because usually the Ca2+ concentration in the cytosol is less than that in the organelles, so when its not it can cause calcium to be actively transported out and reactions to be caused
Pathway of calcium + IP3
- GCPR and/or RTK pathway happens
- The active enzyme cleaves a phospholipid into DAG and IP3
- IP3 binds to a calcium channel and Ca+ goes from the organelle to the cytosol
- the calcium activates cellular responses by binding to calmodulin which activates protein –> responses
What is the enzyme in the calcium called
phospholipase C
What is the name of the phospholipid that gets cleaved in the calcium pathway
PIP2
DAG stands for
diacycloglycerol
What is calmodulin
the protein in the calcium pathway that activates the protein to activate responses
Apoptosis
programmed cell death
Transcription Factors
special proteins that control which genes are turned on (which genes are transcribed into mRNA)
Why can signaling moleucules go through the membrane
because they are either hydrophobic or small enough to cross the hydrophobic interior of the membrane
How do transcription Factors turn on and off
- a hormone binds to a receptor protein in the cytoplasm to activate it
- the protein with the hormone attached goes into the nucleus and sticks onto one gene on a DNA strand
- this gene is turned into mRNA and then leaves the nucleus ot make a protein to stimulate more reactions
How do you see that the signal is transduced in a phosphorylation cascade
the protein changes
Does one signal only illicit one type of response
no one signal can illicit multiple responses because the signal can do different things for different receptors and different proteins
Scaffolding Proteins
large relay proteins which are attached to several other really proteins in order to increase the efficiency of signal transduction pathways by holding all of the proteins close together
Apoptosis
cell suicide –> cellular agents chop up the DNA and fragment the organelles and other cytoplasmic components
How does a cell apoptosis (process)
- death signal molecules binds to receptor
- this inactivates Ced-9 which inhibits Ced-4 and Ced-3
- Ced-3 and Ced-4 become active and they begin the activation cascade to proteases and nucleases which cause apoptosis
- chopping
- cell blebs and the cell components are packaged in besicles that are engulfed and digested by scavenger cells
Is apoptosis dangerous to surrounding cells
no because it packages the digestive enzymes into vesicles so that the digestive enzymes don’t digest other cells or smth
Reasons for apoptosis
to get rid of vistigial cells (like the cells between your toes [webbing] when ur a baby
get rid of cells that are mal and don’t work
Signal Amplification
Each time the signal is transferred to another protein in the phosphorylation cascade, the signal multiplies (WATCH THE VIDEO)
What kind of cell membrane protein can trigger multiple transduction pathways
RTKS
Tyrosine
amino acids that are on the substrate (RTK)
