single vs multi cell signaling?
single-outside world communicate
multi-respond to and other cells
How does local signaling work?
Cell junctions allow signaling molecules to pass freely between adjacent cells.
Cell to cell recognition occurs via cell-surface molecules. (markers on cell) Cells releasing signal to cells in local vicinity for that ligand–able to respond to it
What does long term signaling use?
Hormones
it travels through the bloodstream to reach targets
ability of a cell to respond depends on whether it has a receptor that can bind to that signaling molecule.
Response depends on cells in its membrane– determines response type
What are the 3 stages of cell signaling?
- Reception
- Transduction
- Response
How does reception work?
A receptor protein on the surface of the cell (or inside the cell) binds the signaling molecule (ligand-change in protein shape) and transmits the signal
Binding is very _______and usually causes the receptor to __________
specific
change its shape
What are the 3 types of membrane receptors?
- G protein coupled receptors
- tyrosine kinase receptors
- ion channel receptors
What are G-protein coupled receptors?
Plasma membrane receptors that are associated with G protein. G protein acts like on/off switch.
What are Receptor Tyrosine Kinases?
- membrane receptors with enzymatic activity which attach phosphates to tyrosine residues.
- one RTK may activate 10 or more different pathways
Abnormally activated RTKs associated with?
Many types of cancer
How do Ion Channel Receptors work?
- Binding of ligand causes confrontational change
- when gate opens specific ions can pass through
Why is cellular signaling important?
cells must talk to each other in order to respond to environmental stimuli
Where are intracellular receptors found?
cytoplasm or nucleus
Intracellular Receptors
Signaling molecules must be able to..?
- Pass through the membrane
- steroid hormones
- thyroid hormones
- nitric oxide
What happens during transduction?
- The relay of signals from receptors to target molecules in the cell
- often involves multiple steps
- allows the signal to be amplified
- allows for more regulation
A transduction message is often passed through what?
A change in phosphoralyation. =protein kinases
Dephosphorylation =___________
phosphatese
How does a phosphorylation cascade work?
-Reception- ligand to receptor –>activate protein kinases–>add phosphate—>keeps activating by adding phosphates–> leads to cellular response
What are second messengers?
small, nonprotein, water soluble molecules
-they can easily spread a message throughout the cell
What are the 2 most common second messengers?
- cyclic AMP (cCAMP)
- Calcium ions
What is cAMP?
cyclic adenosine monophosphate
adenylyl cyclase + ATP—->cAMP
What does vibrio cholerae do?
it produces a toxin that causes a G protein to to be unable to hydrolyze GTP to GDP so it remains in “on” position..continually activating cAMP
these increased levels of cAMP causes salt to be excreted into the intestines and water follows=diarrhea
_________is used as a second messenger in both G-protein and tyrosine kinase receptor pathways
Ca2+
What responses does increasing ca2+ have?
- muscle contraction
- secretion
- cell division
