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Cell Communication Chapter 11 Cells need to communicate between themselves to maintain homeostasis. Process by which signal on cell’s surface converted into specific cellular response consists of series of steps - signal-transduction pathway.

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Cell Communication

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Cell Communication

Chapter 11


  • Cells need to communicate between themselves to maintain homeostasis.

  • Process by which signal on cell’s surface converted into specific cellular response consists of series of steps - signal-transduction pathway.


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


  • 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.


  • Also occurs in multicellular organisms.

  • Some cells release local regulators - influence cells in local vicinity.


  • 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.


  • Plants, animals - hormones to signal at greater distances.

  • Cells may communicate by direct contact.

  • Signaling substances dissolved in cytosol pass freely between adjacent cells.


  • 3 stages to signal transduction.

  • 1Reception - chemical signal binds to cellular protein at cell’s surface.

  • 2Transduction - binding leads to change in receptor that triggers series of changes along signal-transduction pathway.

  • 3Response - transduced signal triggers specific cellular activity.


  • 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.


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


  • 1 type - G-protein-linked-receptor.

  • Acts as on/off switch; cycles between being active and inactive.


  • Tyrosine-kinase receptor system helps different systems to function at same time.

  • System activated - activates other systems at same time.


  • 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.


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


  • Some signals diffuse through plasma membrane; don’t need proteins.

  • Some are hormones which act on transcription process.


  • Transduction stage of signal pathway allows for small signal to be amplified - causes large signal.

  • Protein kinases essential - help to initiate responses.


  • Some involve 2nd messengers - molecules small enough to pass through membrane.


http://www.du.edu/~kinnamon/3640/second_messengers/levitan11.2.jpg


  • 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.


http://www.bnl.gov/bnlweb/pubaf/pr/photos/2004/DNAbinding-300.jpg


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


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