cell signalling 1

• What is the main focus of the lecture titled "Cell Signalling I"?

  Understanding cellular components in cell signalling
• What are the types of signalling based on the position of cells?

  Extracellular and intracellular signalling
• How do cells respond to external signals?

  Through transduction and cellular responses
• What changes occur due to signal transduction?

  Phenotypically measurable changes in the cell
• What are the two types of receptors eukaryotic cells use?

  Extracellular and intracellular receptors
• What do extracellular stimuli bind to on the cell membrane?

  Cognate receptors
• What do activated signalling pathways alter?

  Activity of transcription factors
• What do transcription factors bind to in gene promoters?

  Conserved DNA response elements
• What is the role of hydrophobic signaling molecules?

  Bind to cytosolic receptors and enter the nucleus
• How do hydrophilic signaling molecules function?

  Bind to cell-surface receptors and activate transduction
• What do effectors stimulate in the cell?

  Modification of specific cytosolic proteins
• What is the duration of changes caused by effectors?

  Short-term or long-term changes
• What is the purpose of negative feedback in cellular responses?

  Termination or down-modulation of the response
• What are the four classifications of extracellular signalling based on distance?

  Endocrine, paracrine, autocrine, juxtacrine
• How do endocrine signals affect target cells?

  Affect distant target cells via the circulatory system
• What is the role of paracrine signalling molecules?

  Affect only nearby target cells
• What is autocrine signalling?

  Cells respond to signals they secrete
• What is juxtacrine signalling?

  Signals neighbouring cells by direct contact
• What is required for juxtacrine signalling?

  Close contact between adjacent cells
• What do gap junctions allow between animal cells?

  Direct passage of molecules and ions
• What does protein phosphatase do?

  Hydrolyzes phosphate off proteins
• What is the role of protein kinases in signalling?

  Add phosphate from ATP to proteins
• What activates GTP-binding proteins?

  Binding of GTP activates them
• What do GEFs do in GTP-binding proteins?

  Promote GDP dissociation and GTP binding
• What is the function of GAPs in GTP-binding proteins?

  Promote GTP hydrolysis to GDP
• What is the role of the alpha subunit in heterotrimeric G proteins?

  Switches between active and inactive conformations
• What do second messengers do in signal transduction?

  Bind to proteins and modify their behaviour
• What physiological changes can second messengers induce?

  Proliferation, differentiation, migration, survival, apoptosis
• What is the general structure of GPCRs?

  Seven transmembrane α-helical regions
• How many GPCRs are estimated to exist in the human genome?

  Approximately 800 GPCRs
• What is a characteristic of orphan receptors?

  Ligands have not been identified for them
• What should be appreciated about signal transduction?

  It leads to observable changes in targeted cells
• What can changes in signal transduction often be?

  Quantitated or measured
• What are the key components of signal transduction pathways?

  • Receptors (extracellular and intracellular)
  • Signalling molecules (hydrophobic and hydrophilic)
  • Second messengers
  • Effector proteins
  • Transcription factors
• What are the types of extracellular signalling based on distance?

  1. Endocrine
  2. Paracrine
  3. Autocrine
  4. Juxtacrine
• What are the roles of protein kinases and phosphatases in cell signalling?

  • Protein kinases: Add phosphate to proteins
  • Protein phosphatases: Remove phosphate from proteins
• What are the common features of GPCR signal transduction pathways?

  • Seven membrane-spanning α helices
  • Heterotrimeric G protein cycling between GTP-active and GDP-inactive forms
  • Membrane-bound effector proteins
  • Involvement of second messengers
• What physiological changes can result from second messengers?

  • Proliferation
  • Differentiation
  • Migration
  • Survival
  • Apoptosis
• What is the significance of GTP-binding proteins in signalling?

  • Act as on/off switches
  • Cycle between active (GTP-bound) and inactive (GDP-bound) states
• What is the importance of understanding cell signalling in medicine?

  • Disease progression
  • Development of therapies