Cell Communication CHAPTER 11 An Example of Cell

Cell Communication CHAPTER 11

An Example of Cell Communication: Fight or Flight Response http: //learn. genetics. utah. edu/content/begin/cells/cellcom/

Cell Signaling Animal cells communicate by: Direct contact (gap junctions) Secreting local regulators (growth factors, neurotransmitters) Long distance (hormones) Chemical and Electrical signals

Types of Communication: - Autocrine- receptor on same cell (growth factors telling tumor cells to keep growing) - Paracrine- neighboring cell is near signal releasing cell (two neurons) - Juxtacrine- target and releasing cells are in physical contact (quorum sensing in bacteria, gap junctions) - - Endocrine- chemicals that need to travel long distances (hormones)

Signal Transduction Pathway Series of steps by which a signal on a cell’s surface is converted to a specific cellular response Signaling can be short distance or long distance

3 Stages of Cell Signaling: 1. Reception: A signal molecule (ligand) binds to a receptor protein causing it to change shape 2. Transduction: series of molecules interactions that relay signal from receptor to target molecule 3. Response: regulation of transcription or cytoplasmic activities

1. Reception Binding between signal molecule (ligand) + receptor is highly specific. Receptors found in: a) Intracellular receptors (cytoplasm, nucleus) § hydrophobic ligands § Eg. testosterone or other hormones turning on and off certain genes b) Plasma membrane receptor water-soluble ligands

G-Protein-Coupled Receptor https: //www. youtube. com/watch? v=x. T 0 m. AQ 4726 s 2 min

Tyrosine Receptor Kinase https: //www. youtube. com/watch? v=ki. HAdan 2 AOY 1 min

Ligand-Gated Ion Channel http: //www. youtube. com/watch? v=A 1 sdk 7 h y. Gz 8 2 minutes

Plasma Membrane Receptors G-Protein Ligand-Gated Ion Tyrosine Kinase Coupled Channels Receptor (GPCR) 7 transmembrane segments in membrane Attaches (P) to tyrosine G protein + GTP Activate multiple activates enzyme cellular responses cell response at once Signal on receptor changes shape Regulate flow of specific ions (Ca 2+, Na+)

2. Transduction Cascades of molecular interactions relay signals from receptors target molecules; “dominoes effect” Protein kinase: enzyme that phosphorylates and activates proteins at next level Phosphorylation cascade: enhance and amplify signal

Second Messengers small, nonprotein molecules/ions that can relay signal inside cell Eg. cyclic AMP (c. AMP) and Ca 2+ - c. AMP is made when adenyl cyclase converts ATP to c. AMP - c. AMP activates protein kinase A which phosphorylates other proteins

3. Response Regulate protein synthesis by turning on/off genes in nucleus (gene expression) Regulate activity of proteins in cytoplasm

G-Protein-coupled Receptors Figure 6 -11: The G protein-coupled adenylyl cyclase-c. AMP system

Transduction Reviewed Figure 6 -14: Summary of signal transduction systems