1. Cell Communication Chapter 11

2. Cells need to communicate between themselves to maintain homeostasis. Signal-transduction pathway- process by which signal on cell’s surface converted into specific cellular response consists of series of steps.

3. http://www.mpi-dortmund.mpg.de/departments/dep1/signaltransduktion/image3.gif

4. Examples of Cell Communication 1) Yeasts communicate between 2 types of yeast cells to reproduce. 2 sexes, a and alpha - secrete specific signaling molecule, a factor and alpha factor. Factors find each other and bind to each other’s receptors.

6. Also occurs in multicellular organisms. Some cells release local regulators - influence cells in local vicinity.

8. 2) Synaptic signaling - nerve cell produces neurotransmitter that diffuses to single cell - is almost touching sender. Nerve signals travel along series of nerve cells without unwanted responses from other cells.

10. 3) Plants, animals - hormones to signal at greater distances. Cells may communicate by direct contact. Signaling substances dissolved in cytosol pass freely between adjacent cells.

13. 3 stages to signal transduction 1 Reception - chemical signal binds to cellular protein at cell’s surface. 2 Transduction - binding leads to change in receptor that triggers series of changes along signal- transduction pathway. 3 Response - transduced signal triggers specific cellular activity.

15. Receptor proteins present on cells to recognize signal molecules. Ligand - molecule that binds to another molecule, causes cell to change shape when attached to cell’s receptor. Receptors usually found on plasma membrane since signals can’t pass through membrane.

16. http://www.slic2.wsu.edu:82/hurlbert/micro101/images/lock_key.gif

17. Signal Receptor Proteins 3 types: 1) G-protein-linked-receptor - Acts as on/off switch; cycles between being active and inactive. Yeast mating factor, hormones and neurotransmitters use g-Protein- linked-receptors.

20. 2) Tyrosine-kinase receptors - Usually a receptor for a growth factor causing enzyme activity. Helps different systems to function at same time. System activated - activates other systems at same time.

23. 3) Ligand-gated ion channels - Open/close to allow chemical signals to pass through. Important in nervous system - allow Na+ and K+ move into and out of cell.

24. http://dir.niehs.nih.gov/dirln/diricp/figures/overview.jpg

25. Some signals diffuse through plasma membrane; don’t need proteins. Some are hormones which act on transcription process.

27. Transduction stage of signal pathway allows for small signal to be amplified - causes large signal. Protein kinases essential - help to initiate responses.

29. Some involve 2 nd messengers - molecules small enough to pass through membrane. Example: Cyclic AMP (cAMP) Calcium ions (Ca 2+ )

30. Response of particular cell to signal depends on particular collection of proteins. Some pathways actually linked by scaffolding proteins - allows signals to be passed through pathways.

33. All proteins involved in signal pathway are important - defects in any can cause abnormal signals.