Unit 4e Objectives Cell Communication

Unit 4e Cell Communication Learning Objectives 1. List and briefly define the three stages of cell signaling. 1. Reception 1. Signal molecule enters receptor on plasma membrane 2. A signal molecule binds to a receptor protein, causing it to change shape 2. Transduction 1. Molecules are relayed in a transduction pathway 3. Response 1. Cellular response is activated 2. Describe the nature of a ligand-receptor interaction and state how such interactions initiate a signal-transduction system. 1. The binding between signal molecule (ligand) and receptor is highly specific 1. A conformational change in a receptor is often the initial transduction of the signal 3. State where signal receptors may be located in target cells. 1. Intracellular- cytoplasmic or nuclear proteins 2. Small or hydrophobic molecules can readily cross the plasma membrane 4. Compare and contrast G-protein-linked receptors, tyrosine-kinase receptors, ligand- gated ion channels and intracellular hormone receptors. 1. G-protein 1. 2. Tyrosine-kinase 1. 3. Ligand-gated 1. 4. Intracellular hormone 1. 5. List two advantages of using a multistep pathway in the transduction stage of cell signaling. 1. Can amplify a signal 2. Can provide more opportunities for coordination and regulation 6. Describe how phosphorylation propagates signal information and how protein phosphatases turn off signal-transduction pathways. 1. A series of protein kinases add a phosphate to the next one in line, activating it 2. Phosphatase enzymes then remove the phosphates 7. Describe the cAMP second messenger signaling pathway. 1. 8. Explain how the cholera bacterium causes the symptoms of cholera by disrupting G- protein signaling pathways. 1. 9. Describe how the cytosolic concentration of Ca2+ can be altered and how the increased pool of Ca2+ is involved with signal transduction. 1. Other second messengers such as inositol triphosphate and diacylglycerol can trigger an increase in calcium in the cytosol 2. Calcium ions activate the next protein in one or more signal pathways 10.Describe how signal information is transduced into cellular responses in the cytoplasm and in the nucleus. 1. Cytoplasm 1. Signaling pathways regulate a variety of cellular activities 2. 2. Nucleus 1. Regulate genes by activating transcription factors that turn genes on or off 2. 11.Describe how signal amplification is accomplished in target cells. 1. Different combinations of proteins in the cell give the cell great specificity in both the signals it detects and the responses it carries out 12.Explain why different types of cells may respond differently to the same signal molecule. 1. Different receptors can lead to different responses 13.Explain how scaffolding proteins help to coordinate a cell?s response to incoming signals. 1. Scaffolding proteins can increase the signal transduction efficiency 2. Signal response is terminated quickly by the reversal of ligand binding