The plаsmа membrаne is a critical player in cell signaling, bоth because the signal must be transmitted acrоss the membrane, and because phоspholipids in the membrane actually participate in signaling. Although they are present in small quantities, inositol phospholipids, including phosphatidylinositol (or PI, shown at left), are crucial intermediates in multiple signaling pathways. a. PI is modified to create different types of inositol phospholipids. Identify how (what is added) and where (on the molecule, be specific!) PI is modified to create a variety of distinct PI species. b. Identify the enzyme that docks onto an activated receptor tyrosine kinase and produces a particular, specialized PI species in the membrane. c. If receptor tyrosine kinase activation triggers the formation of this particular PI species (based on your answer in b), how does this phospholipid, which is embedded in the membrane, produce an intracellular signal that reaches the nucleus? (hint: your explanation might include the domain that binds to the modified PI species).