Bio exam 230 week 6

  1. Describe the general process of signaling (including signals, receptors, second messengers and final target/effector).
    • 1. Signal
    • — chemical = ligand
    • — ligand is the signal and binds to the receptor
    • 2. Receptors
    • — proteins that sense the signal
    • — when Ligand binds to receptor usually results in conformational change of receptor (protein)
    • 3. Transduction
    • — signal is relayed through the cell using secondary messengers (not proteins)
    • — effector (protein): target of signaling (can be several in a pathway)
    • 4. Final effector: ultimate cellular change
  2. Define protein conformation changes and how conformation changes result in changes in function.
    • Signal (ligand) changes shape of the protein when it binds to the receptor
    • Binding of ligand to receptor is specific and based on shape
    • Receptor conformational (shape) change induces activity
    • The structure typically involved in conformational change is the disruption of R-group bonds resulting in different structural motif interactions
  3. GPCR
    • Integral membrane protein
    • G-Protein Coupled Receptors
    • Iigand binding: outside
    • G-protein binding: inside
    • G-protein includes 3 subunits: alpha betta gamma
    • Conformation change of GPCR after binding ligand triggers binding of GTP to G-alpha
    • Activated G-alpha releases G-betta and G-gamma
    • When betta and gamma are released they act as signaling molecules
    • Both G-alpha and G-betta/G-gamma can further “transduce” the signal
  4. RTK
    • Receptor tyrosine kinase
    • Binding of ligand causes conformational change of the receptor, causing monomers to come together (dimerize)
    • When monomers come together tyrosine kinase domain phosphorylates tyrosines (autophosphorylation)
    • Once activated, the RTK can phosphorylate other proteins
  5. Compare and contrast peptide motifs and structural motifs.
    • Peptide motif: sequence of AA
    • Structural motifs: functional part of protein defined by the secondary structure; cannot function w/o rest of protein
  6. Describe how cAMP is synthesized in the cell.
    • Associated with GPCR pathways
    • Forms the region where ligand will bind
    • After ligand binding the activated G-alpha stimulates enzyme adenylyl cyclase
    • This uses ATP to make cAMP
  7. Describe how DAG/IP3 are synthesized in the cell.
    • Ligand binding causes activation of phospholipase C (PLC)
    • PLC cleaves the fatty acid chains of a phospholipid (PIP2) 
    • This results in IP3 and DAG
    • DAG remains bound to the membrane 
    • IP3 binds to ligand-gated Ca++ channel in ER and causes calcium to enter the cytoplasm, causing a intracellular activity change
  8. Integrate how receptors lead to the production of second messengers.
    • Second messengers continue to transduce the signal in the cell 
    • Primary messengers generates the second messenger; typically generated near the receptor 
    • Second messengers typically interact with a protein (effector) to cause a change
  9. Interpret example signaling pathways from ligand to final target including:
    • Target proteins carry out the response initiated by the signal
    • Final target: biological response; can alter gene expression or alter existing proteins to cause a change
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Bio exam 230 week 6
Week 6