cell signaling Flashcards
What do cells need to do to respond to changes in the environment?
They must be able to receive and process signals from the outside
How does the cell’s ability to respond affect itself?
its ability to tissue repair, protein activity, and apoptosis
what is important about sharing pathways?
they are evolutionary lines of descent
what kinds of distances chould cells communicate over
long and short
what can happen from the same signal
They may have different results
What is a chemical signal?
Signals made inside the body itself in a multicellular animal
(neurotransmitters)
what are mechanical signals
touch
(touch receptors on skin)
what are examples of external chemical signals?
immune response to pathogen
What if the stimulus is a ligand?
it can work as an allosteric regulator
(reversible)
What are some cell-to-cell communication mechanisms?
plasmodesmata and immune cells
what is plasmodesmata?
small pores in plant cells and cell membranes that allow for the cytoplasm to move between cells and exchange info
what are some cell communication ways over short distances
quorum sensing and neurotransmitters
what is an immune cell?
antigen-presenting cell and helper T- Cell
what is quorum sensing?
allows bacteria cells to know when numbers are high, allowing them to do a collective response
- signals turn on and off operons.. conserve energy accessing nutrients and defending against competitors
what are neurotransmitters
chemical signals used to communicate between neurons: dopamine and serotonin.
what are some cell communications over long distances
hormones like testostrone and insluin
what are hormones
chemical signals that are released
what is the signal transduction pathway?
if the cell has a particular receptor capable of detecting a stimulus, it will signal a sequence of molecular events
how can the same signal impact different cells in different ways
ex:
-epinephrine - speed up heart, slow down digestion, initiates glycogen breakdown in liver
what are the three stages of cell signalling
1) reception
2) transduction
3) response
what is reception
when ligands (signal molecules) bind to receptors on cell, which changes the shape of the receptor
where can the receptor be?
it can be..
-extracelluar like G-protein complex
-intracelluar like a small hydrophobic molecule like steroids
what happens when there is a change in the receptor
it starts transduction of signals (cell’s response)
what do cells often have
- hundreds of receptors
-varying specific receptors - combinations of signals to initiate responses
what cells can respond to signals?
only cells with necessary receptors can respond
what is an example of a short-term response?
activate/deactivate an enzyme
what is an example of a long-term response
alter gene expression
what are cell surface receptors
They hit the surface with a cell surface receptor protein and don’t reach the nucleus. They have the hydrophilic signal molecule.
what is an intracellular receptor
it uses a carrier protein to carry a signal molecule that is small and hydrophobic and reaches the nucleus
what is transduction
(convert)
what is a transduction cascade?
an intracellular chemical response to external signal
how does the transduction cascade work?
1) external signal is converted to an internal signal cell which can respond to it (the internal signal cell is usually a TF)
2) Internal signals are amplified (few ligand receptors lead to activation of much more target enzymes)
what does transduction involve
1) secondary messengers are turned on by og receptor that is activated by ligand
- turn on other enzymes
ex: cyclic AMP, calcium, cyclic GMP
2) Phosphorylation cascade -> protein kinases activate other enzymes by phosphorylating them ( adding p)
- cAMP activates protein kinases (PKA) -> phosphorylate proteins (add phosphates) to activate or deactivate enzymes
how is cAMP formed?
The enzyme Adenylyl Cyclase catalyzes the ATP and G-Proteins combine with it, changing the receptor. The Atp becomes cAMP and cAMP acts like a secondary messenger that activates other proteins. cAMP is degraded into AMP which destroys cAMP signal
how cAMP activates protein kinase
cAMP binds to regulatory subunits which dissociate the complex, releasing active catalytic subunits which can phosphorylate target proteins.
what is a protein kinase
an enzyme that catalyzes the transfer of phosphate group from ATP to proteins
how are signals amplified?
many secondary messengers activated by og signals and many protein kinases are activated by that one secondary messenger, which amplifies the of signal
what regulates protein synthesis?
-TF factors which affect transcription
what could the response be?
- regulation of protein synthesis
-regulate protein activity
-modify gene expression
-cellar metabolism
-function
-movement
what does phosphate do?
its an allosteric activator for glycogen phosphorylate which chops up glycogen
what are the three basic receptor pathways
1) g-protein coupled receptors (most common)
2) gated ion channel (channel opens)
3) enzyme-linked receptors (enzymes activated)
how do g-protein-linked receptors work?
the first messenger is a signal molecule like epinephrine which goes to the g protein-coupled receptor which makes a g-protein which has GTP and it goes into the adenylyl cyclase which turns ATP into cyclic AMP which is a secondary messenger which activates protein kinase which then creates a response
how do gated ion channels work?
So at first the ion gated is closed, keeping the ions on the outside but once the ligand connects to the channel, the gate opens which allows the ions to go into the cell, past the plasma membrane which then includes a cellular response, and once the ligand leaves the gate closes
what could the channel gates be used for
muscle cell contractions
what are some siganl pathways in unicellaur
-respond to environemnt
- can communicate with nearby cells
-pheromones can trigger reproduction - external signal triggers movement
what are some multicellular signal pathways
-coordinate activities
-coordinate atvities to support organsim
-> epinephrine
-> temp determination of sex in reptiles
-> apoptosis
-> cell specialization
what are morphogens
they stimulate cell differentiation and development and they are a class of compounds in embryonic development
what happens if signals are blocked
it can lead to deleterious like diseases, diabetes , cancer, posions, pesticides, and pathogens
what are some preventative or prophylactic results if blocked?
anesthetics, antihistamines, birth control
