Signal Transduction Pathway

  1. Cells communicate with one another by means of ___.
    chemical signals
  2. For the receiving cell, there are three stages in the signaling process: __, __, and __.
    reception, transduction, and cell response.
  3. The cell targeted by a particular signal has a receptor molecule complementary to the signal molecule, or __. The ___fits like a key in a lock and triggers a change in the receptor molecule.
    ligand x2
  4. A molecule that binds specifically to a receptor site of another molecule.
  5. __ converts the change in the receptor to a form that can bring about a cellular response. This might involve a series of steps— a ___— that alters and amplifies the change.
    • Signal transduction
    • signal transduction pathway
  6. A mechanism linking a mechanical or chemical stimulus to a specific cellular response.
    signal transduction pathway
  7. In the third stage of cell signaling, the __process brings about a cellular __. This can be any of many different cellular activities, such as activation of a certain enzyme, rearrangement of the cytoskeleton, or activation of specific genes.
    • transduction
    • response
  8. A discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses).
  9. Most __ molecules act on __cells by binding to receptors in the cell membrane. There are several kinds of membrane receptors. Some signal molecules enter target cells and bind to __ in the cytoplasm.
    • signal
    • target
    • intracellular receptors
  10. Many signal molecules, such as __ and many __, act through __. This kind of receptor spans the cell membrane, and works through a protein called a __.
    • neurotransmitters
    • hormones
    • G-protein linked receptors
    • G protein
  11. A chemical messenger released from the synaptic terminal of a neuron at a chemical synapse that diffuses across the synaptic cleft and binds to and stimulates the postsynaptic cell.
  12. In multicellular organisms, one of many types of circulating chemical signals that are formed in specialized cells, travel in body fluids, and act on specific target cells to change their functioning.
  13. A GTP-binding protein that relays signals from a plasma membrane signal receptor, known as a G-protein-linked receptor, to other signal transduction proteins inside the cell. When such a receptor is activated, it in turn activates this protein, causing it to bind a molecule of GTP in place of GDP. Hydrolysis of the bound GTP to GDP inactivates this protein.
  14. When the signal molecule binds to the receptor, the receptor becomes activated. It is now able to activate a specific __ by causing __to displace GDP on the __. The activated __then binds to another protein, usually an enzyme, and alters its activity. Then the __ hydrolyzes its __ and reverts to its inactive form— ready to respond to another signal.
    • G protein
    • GTP
    • G protein
    • G protein
    • G protein
    • GTP
  15. __signal cells to grow and divide by acting though __.
    • growth factors
    • receptor tyrosine kinases
  16. protein that must be present in the extracellular environment (culture medium or animal body) for the growth and normal development of certain types of cells; a local regulator that acts on nearby cells to stimulate cell proliferation and differentiation.
    growth factor
  17. Binding of signal molecules causes two polypeptides to join, activating parts of each that act as ___, which then phosphorylate tyrosines in the tail of the other polypeptide.
    The receptor protein is now recognized by specific __ proteins inside the cell. One __ may activate several relay proteins at once, triggering several different effects within the cell.
    • tyrosine-kinase enzymes
    • relay
    • receptor tyrosine kinase
  18. Some membrane receptors are __. They are protein pores in the plasma membrane that allow or block the passage of certain ions through the membrane. For example, this occurs when one neuron signals another via a neurotransmitter.
    ligand-gated ion channels
  19. A nerve cell; the fundamental unit of the nervous system, having structure and properties that allow it to conduct signals by taking advantage of the electrical charge across its cell membrane.
  20. An atom that has gained or lost electrons, thus acquiring a charge.
  21. The signal molecule attaches to a site on the __. This changes the shape of the protein, opening a channel through the membrane. Ions flow through the channel, and the change in ion concentration triggers a cellular response.
    ion channel protein
  22. Some signal molecules actually enter target cells and act on ___— proteins located inside the target cell. __ like testosterone and estrogen act on __.
    • intracellular receptors
    • Steroid hormones
    • intracellular receptors
  23. Nonpolar molecules like __ and __ are able to pass through the plasma membrane and bind to a receptor protein in the cytoplasm or nucleus of a target cell. The activated receptor triggers a change in the cell. __ cause receptors to turn genes on and off.
    • steroids
    • thyroid hormones
    • Steroids
  24. A type of lipid characterized by a carbon skeleton consisting of four rings with various functional groups attached.
  25. An endocrine gland, located on the ventral surface of the trachea, that secretes two iodine-containing hormones, triiodothyronine (T3) and thyroxine (T4), and calcitonin.
    thyroid gland
  26. In multicellular organisms, one of many types of circulating chemical signals that are formed in specialized cells, travel in body fluids, and act on specific target cells to change their functioning.
  27. Receptors that are plasma-membrane proteins usually affect the cell through multistep __. These pathways allow for amplification of signals and signal __ and __. __ often involves smaller molecules called second messengers and protein phosphorylation by enzymes called __.
    • signal transduction pathways
    • coordination and regulation
    • Signal transduction
    • protein kinases
  28. A mechanism linking a mechanical or chemical stimulus to a specific cellular response.
    signal transduction pathway
  29. A small, nonprotein, water-soluble molecule or ion, such as calcium ion or cyclic AMP, that relays a signal to a cell’s interior in response to a signal received by a signal receptor protein.
    second messenger
  30. An enzyme that transfers phosphate groups from ATP to a protein.
    protein kinase
  31. __ are small non-protein molecules that act as intermediaries in signal transmission. Two important second messengers are __ and __.
    • second messengers
    • cyclic AMP
    • calcium ions
  32. Cyclic adenosine monophosphate, a ring-shaped molecule made from ATP that is a common intracellular signaling molecule (second messenger) in eukaryotic cells (for example, in vertebrate endocrine cells). It is also a regulator of some bacterial operons.
    cyclic AMP (cAMP)
  33. __ acts as a second messenger in pathways initiated by both __ and __.
    The hormone epinephrine acts via __ as a second messenger. An epinephrine molecule docks with a receptor protein, which acts through a G protein to activate the enzyme __, which converts ATP into __, which quickly diffuses through the cell and triggers further steps in the signaling pathway.
    • Cyclic AMP
    • G-protein-linked receptors
    • receptor tyrosine kinases
    • cyclic AMP
    • adenylyl cyclase
    • cyclic AMP (cAMP)
  34. A catecholamine hormone secreted from the adrenal medulla that mediates fight-or-flightresponses to short-term stress; also functions as a neurotransmitter.
  35. An enzyme that converts ATP to cyclic AMP in response to a chemical signal.
    adenylyl cyclase
  36. An enzyme that transfers phosphate groups from ATP to a protein.
    protein kinase
  37. __ also act as second messengers in signal transduction pathways.
    The signal molecule docks with the receptor and activates an enzyme called phospholipase C. The enzyme cleaves a small molecule called ___ from a certain kind of membrane phospholipid. __docks with a __channel on the endoplasmic reticulum. The channel opens, releasing calcium ions into the cytoplasm, where they activate proteins that carry out cell responses.
    • Calcium ions
    • inositol trisphosphate— IP3
    • IP3
    • calcium
  38. A second messenger that functions as an intermediate between certain nonsteroid hormones and a third messenger, a rise in cytoplasmic Ca2+ concentration.
    inositol trisphosphate (IP3)
  39. Enzymes called __ are important links in many signal transduction pathways.
    protein kinases
  40. What does a protein kinase do?
    More often than not, the activated protein is also a __, which may act on still another __. One kinase may activate many molecules of the next type of kinase in the chain, thus amplifying the signal, until the last kinase activates many molecules of the protein that carries out the final cellular response.
    • catalyzes the transfer of phosphate groups from ATP to another protein.
    • protein kinase x2
  41. A __ ultimately sets in motion some cellular response, such as alteration of metabolism, rearrangement of the cytoskeleton, or modulation of gene activity.
    signal transduction pathway
  42. An extensively branched glucose storage polysaccharide found in the liver and muscle of animals; the animal equivalent of starch.
  43. Here's an example of how signal transduction affects metabolism. The fight-or-flight hormone, epinephrine, causes the liver to do what?
    In a liver cell, epinephrine acts by triggering a cascade of __, which eventually activate molecules of the enzyme __. This enzyme cleaves glycogen molecules, releasing sugar in the form of glucose-1-phosphate.
    • release sugar into the blood for energy
    • protein kinases
    • glycogen phosphorylase
  44. A protein kinase might activate a gene and trigger the synthesis of a new protein. What can the protein then do?
    The protein then redirects cell metabolism.
Card Set
Signal Transduction Pathway
Cell communication