Cell Signaling Lecture 25 BSCI 420/421 Oct 30/31, ’02 The 4 Laws
15 Slides999.50 KB
![](/assets/img/1/cell-signaling-lecture-25-bsci-420-421-oct-30-31-02-the-4-laws/page-0.jpg)
Cell Signaling Lecture 25 BSCI 420/421 Oct 30/31, ’02 The 4 Laws of Ecology: “All things are interconnected. Everything goes somewhere. There’s no such thing as a free lunch. Nature bats last.” -Earnest Callenbach A. General principles of Cell Signaling B. Signaling thru cell surface receptors
![](/assets/img/1/cell-signaling-lecture-25-bsci-420-421-oct-30-31-02-the-4-laws/page-1.jpg)
o cell signaling allows organisms to coordinate the activity wide variety of different cell types. eneral principles of cell to cell signaling. can communicate via signal molecules in 4 different ways: r in distance over which they act. st: e.g. Boss & Sevenless. E.g. Inductive dev. signals
![](/assets/img/1/cell-signaling-lecture-25-bsci-420-421-oct-30-31-02-the-4-laws/page-2.jpg)
E.g. neurotransmitters E.g. Insulin
![](/assets/img/1/cell-signaling-lecture-25-bsci-420-421-oct-30-31-02-the-4-laws/page-3.jpg)
Receptors for signal Molecules can be either: Cell surface Signal mols are water soluble E.g. peptide hormones Induce cytoplasmic signal cascade Or Intracellular Signal molecules are hydrophobic e.g.steroids Carriers in bloodstream
![](/assets/img/1/cell-signaling-lecture-25-bsci-420-421-oct-30-31-02-the-4-laws/page-4.jpg)
A simple signaling pathway or cascade induced by binding To a cell surface receptor Fig.15-1
![](/assets/img/1/cell-signaling-lecture-25-bsci-420-421-oct-30-31-02-the-4-laws/page-5.jpg)
Signal molecules that bind to intracell receptors, and hence genes. All small & hydrophobic Fig 15-12
![](/assets/img/1/cell-signaling-lecture-25-bsci-420-421-oct-30-31-02-the-4-laws/page-6.jpg)
Nuclear receptors The DNA-binding domains Contain multiple Zinc
![](/assets/img/1/cell-signaling-lecture-25-bsci-420-421-oct-30-31-02-the-4-laws/page-7.jpg)
An animal cell depends on multiple extracellular signals
![](/assets/img/1/cell-signaling-lecture-25-bsci-420-421-oct-30-31-02-the-4-laws/page-8.jpg)
B. Signaling thru Cell Surface Receptors 3 Classes of Cell Surface Receptors e.g Ach receptors e.g. epinephrine r
![](/assets/img/1/cell-signaling-lecture-25-bsci-420-421-oct-30-31-02-the-4-laws/page-9.jpg)
Types of surface receptors, cont. e.g. Growth factor receptors
![](/assets/img/1/cell-signaling-lecture-25-bsci-420-421-oct-30-31-02-the-4-laws/page-10.jpg)
Too much stimulation can be a problem. Cells need to be able to respond to changes in signal over a wide range of conc Target cells can become desensitized in 5 diff ways:
![](/assets/img/1/cell-signaling-lecture-25-bsci-420-421-oct-30-31-02-the-4-laws/page-11.jpg)
G-protein-linked receptors The largest and most widespread family of cell surface receptors, found in all eukaryotes. 7- pass transmembrane proteins
![](/assets/img/1/cell-signaling-lecture-25-bsci-420-421-oct-30-31-02-the-4-laws/page-12.jpg)
Associate with a trimeric G Protein (GTPase)
![](/assets/img/1/cell-signaling-lecture-25-bsci-420-421-oct-30-31-02-the-4-laws/page-13.jpg)
Activated Receptor acts As a GNEF. The alpha subunit Exchanges GTP For GDP The other 2 s-units Dissociate from Alpha, and both Diffuse away in an Active state
![](/assets/img/1/cell-signaling-lecture-25-bsci-420-421-oct-30-31-02-the-4-laws/page-14.jpg)
Activation of target protein e.g. adenylyl Cyclase Hydrolysis Of GTP Formation of The inactive trimer