Bio 111 Study Guide Chapter 11 Cell Communication BEFORE CLASS: Reading: Read the introduction on p. 210, and for Concept 11.1, read from the first full paragraph on p. 212. Read all of Concept 11.2. Pay special attention to Figure 11.8 which describes the three main types of transmembrane receptors. Read Concept 11.3 to the end of the section on cyclic AMP on p. 221. Read the first few paragraphs of Concept 11.4 on p. 223 (just until the end of the first column). Skip the rest of the chapter (Concept 11.5 on Apoptosis is fascinating, but we won t have time for it.) Definitions: signal transduction pathway hormones reception transduction response relay protein/molecule ligand receptor G-protein-coupled receptor (GPCR) G protein receptor tyrosine kinases (RTKs) dimer phosphorylation ligand-gated ion channel protein kinase protein phosphatase second messengers
Questions/Problems: 1. Use each of the words below once to label a part of the figure. Receptor Cytoplasm Relay molecules Transduction Response Reception Activation of cellular response Signaling molecule (ligand) Plasma membrane RET Gene Case Study: The RET gene codes for a receptor tyrosine kinase protein like the ones you read about in this chapter. It is one of the cell-surface molecules that can transduce signals for normal cell growth and differentiation during embryonic development. (RET s function in adults isn t understood yet.) The RET protein spans the cell membrane, so that one end of the protein remains inside the cell and the other end projects from the outer surface of the cell. This positioning of the protein allows it to receive signals that allow the cell to respond to its environment. During embryonic development, when certain growth factors bind to the RET protein, it triggers a complex cascade of chemical reactions inside the necessary cells. These reactions instruct the cell to undergo certain changes, such as dividing or maturing to take on specialized functions.
DURING CLASS: Local and Long-Distance Signaling Local Signaling: Long-distance Signaling: Regulation of Proteins Protein Kinase Protein Phosphatase Signal Transduction Pathways Reception Ligand Receptor G Protein-Coupled Receptors (GPCRs):
Receptor Tyrosine Kinases (RTKs): Ligand-gated Ion Channel Receptors: Intracellular Receptors: RET Gene Case Study: The RET protein is a receptor tyrosine kinase that consists of a receptor in the extracellular region, a hydrophobic transmembrane domain, and two intracellular tyrosine kinase domains (see figure on the right). from: nature.com During embryonic development, when the ligand (a growth factor) binds to the receptor part of RET proteins in the plasma membrane of cells of the neural crest, it causes two neighboring RET proteins to form a dimer. Each RET s tyrosine kinase region phosphorylates specific tyrosines on the other, using phosphates from ATP molecules. The RET proteins are then fully activated. Inactive relay proteins diffuse, bind to them, and become activated. They then relay the signal to the cell that it is time to grow and become specialized into nerve cells of the peripheral nervous system (including those found in the stomach and intestines, kidneys, adrenal glands, thyroid, and parathyroid). V804L Mutation of RET: The V804L mutation alters an ATP binding site in the tyrosine kinase domain of the RET protein. This causes abnormal phosphorylation of the relay proteins that are specific to that pathway. What affect do you think this abnormal phosphorylation of the relay proteins has on the cell?
Transduction Phosphorylation Cascade: Second Messengers: Response In the nucleus: In the cytoplasm: ** Take Away Concept ** Signal transduction pathways are complex but awesome. They are essential to the right messages getting to the right cells at the right time.
AFTER CLASS: Questions/Problems: 1. Nerve growth factor (NGF) is a water-soluble signaling molecule. Would you expect the receptor for NGF to be intracellular or in the plasma membrane? Why? 2. Fill in the blanks: A. When a kinase phosphorylates another protein, this usually the protein. B. Steroid hormones are which allows them to easily cross the plasma membrane. C. Neurotransmitters are an example of signaling molecule. D. A G protein is when GTP is bound to it. E. function as long-distance signal molecules in both plants and animals. 3. Briefly describe how each of these receptors receives its signal and passes it on to the cell. a. G Protein-coupled Receptors: b. Receptor Tyrosine Kinases: c. Ligand-gated Ion Channel Receptors: d. Intracellular Receptors (steroid):