Cellular Communication

  1. Extracellular Matrix
    • Found in animal tissues
    • The "stuff" found outside of the cell
  2. Whats outside the cell membrane?
    • Extracellular matrix (ECM)
    • Cell Walls
  3. Main components of the extracellular matrix
    • Collagen
    • Proteglycans
  4. Functions of the extracellular matrix
    • Support
    • Segregate tissues (components differ through tissues)
    • Regulation of intercellular communication
  5. Chondrocytes are cells found in the cartilage in our joints. In some forms of osteoarthritis, destruction of the chondrocyte extracellular matrix is associated with a diseased endoplasmic reticulum. This supports the idea that _____.
    Endoplasmic reticulum is involved in the synthesis of extracellular matrix
  6. Where are cell walls found
    • Plants (don't have extracellular matrix)
    • Bacteria
    • Fungi
    • Some protists
  7. Major functions of cell walls
    • Protection (rigid surface)
    • Maintain shape
    • Prevent excess water uptake
  8. Main component of cell walls
    Cellulose (polymer of glucose that doesn't break)
  9. What is the middle lamella
    What holds two cell walls together (pb between the bread)
  10. Tight junctions
    • Form water tight seals between cells
    • Restricts passive movement
    • -can vary between tissues
    • -dynamic (they can expand and contract)
  11. Three types of connection and communication between adjacent cells
    • Tight Junctions
    • Desmosomes
    • Gap Junctions
  12. Desmosomes
    • Bind the cytoskeletons of adjacent cells together
    • Cell-cell adhesions are selective`
  13. Cadherins
    • Proteins in desmosomes that link cells
    • Type varies between tissues
  14. "Rivets" that connect the cytoskeletons of two adjacent cells together so they resist being pulled apart are called ____.
  15. Gap junction (animals)
    • Membrane proteins line up to form channels between cells
    • Allows passage of ions and small molecules
  16. Plasmodesmata (plants)
    • Membrane-lined channels through cell wall connect adjacent cells 
    • Allowing things to move between cells
  17. Long-distance signaling
    • Uses hormones (endocrine signaling)
    • Travel through bloodstream to reach target cells
    • Ability of cell to respond depends on whether it has receptors that can bind the signaling molecule
    • Example: Adrenaline (epinephrine)-- fight or flight
  18. 3 stages of cell signaling
    • Reception
    • Transduction
    • Response
  19. Reception
    • The signal is detected by the cell.
    • A receptor protein on the surface of the cell (or inside the cell) binds the signaling molecule (ligand) and transmits the signal
    • Binding is very specific and causes the receptor to change its shape
  20. Transduction
    • The signal is converted into a form that can cause some type of cellular response
    • -Activates enzyme to produce 2nd messengers
    • -Activate phosphorylation cascade
  21. Response
    • The cell responds in some way to the signal
    • Whole point of the signal is to tell the cell to do something
    • -change in gene expression (protein synthesis) which means turn a gene on/off
    • -regulate the activity of a protein (i.e open an ion channel)
  22. Three main types of membrane receptors
    • G protein-coupled receptors
    • Tyrosine kinase receptors
    • Ion channel receptors
  23. G protein-coupled receptors (GPCRs)
    Plasma membrane receptors that are associated with G proteins
  24. What does a G protein act as?
    • On/off switch
    • -When GTP is bound= on
    • -When GDP is bound= off
    • Contains GTPase domain
    • -Shuts itself off
  25. A mutant form of G protein lacks the ability to function as a GTPase. What effect do you think this would have?
    The G protein will be constitutively active
  26. Receptor Tyrosine Kinases (RTKs)
    • Membrane receptors with enzymatic activity which attach phosphates to tyrosine residues
    • Activates Ras (G protein)
  27. What is associated with many types of cancer?
    • Abnormally activated RTKs 
    • Lots of different pathways that can be activated by the receptors
  28. Ion Channel Receptors
    • Binding of ligand causes conformational change
    • When gate opens specific ions can pass through
  29. Intracellular receptors
    • Signaling molecule must be able to pass through the membrane
    • -steroid hormones
    • -thyroid hormones
    • -nitric oxide
    • Binds to receptor (in cytoplasm)
    • -transported to nucleus
    • -trigger change in gene expression
  30. What characteristic allows some signaling molecules to pass through the membrane to deliver their message?
  31. Steps of transduction
    • Allows the signal to be amplified
    • Also allows for more regulation
  32. How are messages often passed along in transduction?
    • A change in protein conformation
    • -Phosphorylation= protein kinases
    • -Dephosphorylation= protein phosphatases
  33. Second Messengers
    • Small, non-protein, water-soluble molecules
    • -can easily spread messages throughout cells
  34. Two most common second messengers:
    • Cyclic AMP (cAMP)
    • Calcium ions (Ca2+)
  35. What happens if there are high levels of cAMP
    Causes salt to be excreted into the intestines and water follows= diarrhea
  36. Ca2+
    Used as a second messenger in both G-protein and tyrosine kinase receptor pathways
  37. What kind of responses come from increasing Ca2+ concentrations
    • Muscle contraction
    • Secretion
    • Cell division
  38. Is Ca2+ actively transported or passively transported?
  39. What does the active transcription factor do?
    They transcribe the gene and tell the DNA to start making something or stop making something
  40. What would be inhibited by a drug that specifically blocks the addition of phosphate groups to proteins?
    Receptor tyrosine kinase activity
  41. Which of the following best describes a signal transduction pathway?

    A. Sequence of changes in a series of molecules resulting in a response
  42. All cells in your body contain the same DNA so why is a heart cell different from a liver cell?
    • Different genes are turned on in different cells
    • -different cells therefore have different proteins
  43. Crosstalk
    Multiple pathways interact to modify response
  44. What must happen in order to respond to new signals?
    • Old signals must be shut off
    • Binding of signaling molecules to receptors is reversable
  45. What happens when you reverse a signaling molecule?
    • The messengers return to their inactive form
    • -GTP hydrolyzes to GDP
    • -cAMP is converted to AMP
    • -Phosphatases remove phosphates to deactivate proteins
  46. Which of the following is true of transcription factors?

    B. they control gene expression
  47. Insulin is a peptide hormone produced by the pancreas. Even though it circulates throughout the bloodstream, it affects only certain cells and tissue. This data would suggest that
    Target specificity is determined at the level of a receptor
  48. What effect would you expect an inactive phosphatase to have on a signaling pathway?
    The pathway would be constitutively active
Card Set
Cellular Communication