BIO Exam 3

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  1. What is a ligand?
    A signaling molecule
  2. What is a receptor protein?
    Is a molecule to which the signal (ligand) binds.
  3. Cells can communicate through any of four basic mechanisms. Name them:
    • Direct contact
    • Paracrine signaling 
    • Endocrine signaling
    • Synaptic signaling
  4. What are Paracrine siganls?
    Signals with short lived, local effects.
  5. Define a hormone.
    A long-lived signal molecule enters the circulatory system.
  6. Define endocrine signaling.
    A type of intercellular communication that uses hormones, Both plants and animals use this signaling mechanism extensively.
  7. In animals, the cells of the nervous system use signal molecules called _______. They do not travel through the circulatory system.
  8. What is a chemical synapse?
    The association of a neuron and its target cell.
  9. What is synaptic signaling?
    The type of intercellular communication that uses neurotransmitters via a chemical synapse.
  10. Define signal transduction.
    The events that occur within the cell on receipt of a signal. These events form a discrete pathway that lead to a cellular response to the signal received by receptors.
  11. *a major source of control for protein function is the addition or removal of phosphate groups, called phosphorylation or dephosphorylation, respectively.
  12. What are phosphatases?
    A class of enzymes that removes phosphate groups, reversing the action of kinases. A protein activated by kinase can be deactivated by a phosphatase.
  13. Intracellular receptors bind _______ ligands , and cell surface or membrane receptors bind _______ ligands.
    • hydro-phobic,
    • hydrophylic
  14. *Cell communication involves chemical signals, or ligands, that bind to cellular receptors.
  15. *Binding of ligand to receptor initiates signal transduction pathways that lead to a cellular response.
  16. *Different cells may have the same response to one signal and the same signal can also elicit different responses in different cells.
  17. *The phosphorylation-dephosphorylation of proteins is a common mechanism of controlling protein function found in signaling pathways.
  18. What is an Ion Channel?
    A protein that has a pore in its center that connects the extra-cellular fluid with , the cytoplasm. The pore is big enough for the ions to pass through, so the the protein functions as an ion channel.
  19. What are protein kinases?
    enzymes that add phosphate groups to proteins.
  20. What is a G protein?
    it binds the nucleotide guanosine triphosphate (GTP). The ligand binds to the receptor, activating it, which activates the G protein, which in turn activates the effector protein.
  21. What is the function of second messengers?
    They are small molecules that alter the behavior of cellular proteins by binding to them and changing their shape.
  22. *Receptors may be internal (intracellular receptors) or external (membrane receptors).
  23. *Membrane receptors include channel-linked receptors, enzymatic receptors, and G-protein-coupled receptors.
  24. *Signal transduction through membrane receptors often involves the production of a second signaling molecule, or second messenger, inside the cell.
  25. *Hydropobic signaling molecules can cross the membrane and bind to intracellular receptors.
  26. *The steroid hormone receptors act by directly influencing gene expression.
  27. *The steroid hormone receptors act by directly influencing gene expression.
  28. *On binding hormone, the hormone-receptor moves into the nucleus to turn on (or sometimes turn off) gene expression. This also requires another protein called a coactivator that functions with the hormone-receptor.
  29. *The cell's response to a hormone depends on the presence of a receptor and coactivators as well.
  30. *Receptor tyrosine kinases (RTK) are membrane receptors that can phosphorylate tyrosine.
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BIO Exam 3

Ch. 9,10,11,12
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