1 / 23

Chapter 11 Cell Communication

Chapter 11 Cell Communication. You Must Know. 3 stages of cell communication Reception, transduction, & response How G-protein-coupled receptors receive cell signals & start transduction How receptor tyrosine kinase receive cell signals & start transduction

mignonj
Download Presentation

Chapter 11 Cell Communication

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Chapter 11Cell Communication

  2. You Must Know • 3 stages of cell communication • Reception, transduction, & response • How G-protein-coupled receptors receive cell signals & start transduction • How receptor tyrosine kinase receive cell signals & start transduction • How a cell response in the nucleus turns on genes while in the cytoplasm it activates enzymes • What apoptosis means & why it is important to normal functioning of multicellular organisms

  3. 11.1 • External signals are converted into responses within the cell • Animal cells communicate: • by direct contact • by secreting local regulators (growth factors or neurotransmitters)

  4. 3 stages of cell signaling: • 1) Reception: • The target cell’s detection of a signal molecule coming from outside the cell • 2) Transduction: • Conversion of the signal to a form that can bring about a specific cellular response • 3) Response: • Specific cellular response to the signal molecule

  5. 11.2 • Reception: a signal molecule binds to a receptor protein, causing it to change shape • The binding between a signal molecule (LIGAND) & a RECEPTOR is highly specific • A change in the shape is the initial transduction of the signal

  6. Receptors are found in 2 places: • 1) Intracellular • Inside membrane in the cytoplasm or nucleus • Signal molecule MUST cross the membrane (hydrophobic) : examples – steroids & NO • 2) Plasma membrane receptors • Bind to water-soluble ligands

  7. 3 types of plasma membrane receptors: • 1) G-Protein-Coupled receptor • 2) Receptor tyrosine kinase • 3) Ligand-gated ion channels

  8. 1) G-Protein-Coupled receptor • Step 1 • The ligand (signaling molecule) has bound to the G-protein-coupled receptor • Causes a conformational change in the receptor so it can bind to an inactive G-protein • This causes a GTP to displace the GDP • This activates the G-protein • Step 2 • The G protein binds to a specific enzyme & activates it • When activated, it triggers the next step in a pathway leading to cellular response • All shape changes are temporary • To continue, new molecules are required

  9. 2) Receptor tyrosine kinase • Step 1 • Shows binding of signal molecules to the receptors & formation of a dimer • Each tyrosine kinase adds a phosphate from an ATP • Step 2 • Fully activated receptor protein that initiates a unique response • The ability of a single ligand to activate multiple responses is the difference between #2 & #1

  10. 3) Ligand-gated ion channels • Caused by specific signal molecules • Opens & closes to regulate the flow of specific ions - Na+ or Ca2+

  11. 11.3 • Transduction – Multiple molecular interactions relay signals from receptors to target molecules • Involve a phosphorylation cascade • Usually a multistep pathway • Leads to greater amplifying of the signal • Enzymes called protein kinases phosphorylate & activate proteins • Allows for a greater cellular response

  12. Not all components are proteins • May include small, nonprotein water-soluble molecules or ions called SECOND MESSENGERS • Calcium ions & cyclic AMP are examples • Once activated, they can initiate a phosphorylation cascade

  13. 11.4 • Response – Cell signaling leads to regulation of transcription or cytoplasmic activities • Many pathways regulate protein synthesis • Done by turning specific genes on or off in the nucleus • The final activated molecule in a signaling pathway functions as a transcription factor

  14. In the cytoplasm • Signaling pathways often regulate the activity of proteins rather than their synthesis • Example: final step in signaling pathway may affect the activity of enzymes or cause cytoskeleton rearrangement

  15. 11.5 • Apoptosis – integrates multiple cell signaling pathways • Controlled cell suicide • The cell is systematically dismantled & digested • Protects neighboring cells from damage that would occur if a dying cell leaked out its enzymes

  16. Apoptosis • Triggered by signals that activate a cascade of suicide proteins in the cells • In vertebrates, a normal part of development: • Normal nervous system • Operation of immune system • Normal morphogenesis of hands & feet in humans

More Related