Discussion 2 – in class activity 1 Form groups and work through these questions together. Feel free to use the internet, your notes, or any other resource that is helpful in answering these questions. Ask your TA or UTA if you’re stuck. You’ll go over these questions at the end of your discussion section. If you finish early, begin working on the discussion homework which is due by Sunday night. 1. Phosphorylation and dephosphorylation are important processes in cell signaling and one way that proteins, such as enzymes or transcription factors, are turned on and off. 2. Find one example of a stem cell that could be found in a non-pregnant, adult, human body. Where is this cell found? What role does it play? What is its level of potency? 3. What does gene expression mean? a. What does phosphorylation mean? b. What is the source of the phosphate? c. How does phosphorylation lead to changes in protein activity? d. What type of macromolecule (DNA, lipid, carbohydrate or protein) is a phosphatase? e. What does a phosphatase do?Discussion 2 – in class activity 2 Use this diagram for the following question The cells above show a receptor kinase pathway without a signal present (left) and with the signal (right). You analyze cells with this pathway and observe the following results. • The receptors are present • TK1 molecules are not phosphorylated • TFA molecules are in the cytoplasm and inactive. Is this signal bound to the receptor (either currently or very recently)? Explain your answer in one sentence. S = Signal R = Receptor TK1= tyrosine kinase 1 PO4 = phosphate group TK2= tyrosine kinase 2 TFa = transcription factor a RNAp = RNA