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How are singals received:
- Receptor proteins
- 1) on cell (in membrane) surface
- 2) in cell
- Message goes to end (not signal)
- 1) reception of signal (ligand)
- 2) Signal transduction
- 3) Cell response
Types of cell signals:
1) ligand has local effects, short lived (paracrine signals) early development
2) ligand has distant effects, ligand is a hormone (endocrine signals) hormone travels in blodd, hormone travels in xyloem, phloem in plants.
3) synaptic signaling (nerve cell involved) nervous system
4) direct contact (cell right next to eachother)
If receptor is internal - it has to pass membrane (lipid soluble, estrogen, testosterone, vitamin D
synaptic signaling (nerve cell involved) nervous system
ligand has local effects, short lived early development
- distant effects, ligand is a hormone.
- hormone travels in blood and in xyloem,phloem in plants
nerve cell involved/nervous system
Receptor cell is internal:
- lignd is lipid soluble/ gene regulators
- singal enters cell,
- attaches to receptor,
- rec drops off the inhibitor,
- rec moves into nucleus,
- gene activity changed
- most on cell surface
- a) enzyme receptor -act as kinase - adds phosphate group to another molecule
b) chemically gated ion molecule (nervous system)
- c) G protein couple receptor (GPCR's)
- Binds signal on outside
- Gprotein on inside activated-goes and does something
- how message gets put to work (G-Protein coupled receptor)
- 1) CAMP (adenosine mono phosphoate) used by animal cells
- 2) Ca++ ion (calcium ions) (aniaml/plants)
example: epinephrine as signal (fight/flight)
epinephrine binds to receptor --> activates G protein --> makes Cyclic AMP ---> Activate kinase---> results in muscle and liver cells--> gylcogen-->glucose
- results vary in diff cells
- "signal can have different results in diff cells"
- "2 signals can do same thing"
calcium ions (animals/plants)
- cascade of reactions:
How are signals amplified:
Tight Junction: act as a wall, keeping molecules on one side or the other.Anchoring Junctions: attach to cytoskeletona)
Desmosome - cytoskeleton of adjacent cellsb) Adherins - connect actin filament
Gap Junctions: small enough to allow passage of small substances in animals.
Plasmodesmata: communicate through cell walls in plants