1. Cell surface receptor proteins act as the transducers of cell signaling information, converting extracellular signals to intracellular signals. a.) List & Describe the 3 general types of cell surface receptors involved in cell signaling cascades. b.) The binding of cell surface receptor to it’s ligand is the 1st step in a signal transduction pathway which ultimately results in the activation of many cytoplasmic proteins in a step-wise fashion. Explain 2 reasons why this method of signaling is advantageous for a cell. [Hint: Why doesn’t the cell respond after just one event? ] 2. You are examining the cellular response to a new drug. You treat cells with the drug and measure the intracellular levels of cAMP and find that they increase as a response to the treatment. With what type of receptor would you predict the drug interacts and give an example of how is the rise in intracellular cAMP used to change cellular physiology or metabolism? 3. A. When studying the cancer cells you discover that there is high Ras activity in the cells, but you can find no mutations in the Ras gene. You then start investigating different Receptor Tyrosine Kinases. You find by immunofluorescence, using a monoclonal antibody against the kinase domain, that one specific RTK is now located throughout the cytosol instead of in the plasma membrane. You then perform Western blot analysis on protein extracts from these cancer cells, and find that the RTK is much larger than normal. What kind of mutation in the RTK is indicated by these results, and how does that specific type of mutation lead to cancer? B. The normal function of the Rb gene (that is mutated in retinoblastomas) is to regulate cell cycle progression through control of a family of transcription factors called E2F. The general pathway Rb is involved in is shown below. p16 --| Cyclin D/Cdk4 --| Rb --| E2F → upregulation of S phase genes Which of the genes in this pathway are potential tumor suppressor genes and why?