* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Cell_Communication_Lecture_2016
Survey
Document related concepts
Cellular differentiation wikipedia , lookup
Phosphorylation wikipedia , lookup
Endomembrane system wikipedia , lookup
Hedgehog signaling pathway wikipedia , lookup
Cytokinesis wikipedia , lookup
Tyrosine kinase wikipedia , lookup
Nuclear magnetic resonance spectroscopy of proteins wikipedia , lookup
Protein phosphorylation wikipedia , lookup
Biochemical cascade wikipedia , lookup
G protein–coupled receptor wikipedia , lookup
List of types of proteins wikipedia , lookup
Transcript
Cell Communication AP Biology Chapter 11 Communication Methods Cell-to-cell contact Local signaling Long distance signaling AP Biology Cell-to-Cell Communications Cell junctions directly connect the cytoplasm of adjacent cells Ex: cardiac cells for rhythmicity; plamodesmata between plant cells Surface receptors can give/send information Ex: specific immune response Plasma membranes Gap junctions between animal cells AP Biology Plasmodesmata between plant cells VIDEO Local Signaling VIDEO Adjacent cells are signaled. Chemical messengers released Ex: Neurotransmitters via neurons Local signaling Target cell Electrical signal along nerve cell triggers release of neurotransmitter Neurotransmitter diffuses across synapse Secretory vesicle Local regulator diffuses through extracellular fluid (a) Paracrine signaling. A secreting cell acts on nearby target cells by discharging molecules of a local regulator (a growth factor, for example) into the extracellular fluid. AP Biology Target cell is stimulated (b) Synaptic signaling. A nerve cell releases neurotransmitter molecules into a synapse, stimulating the target cell. Yeast Sexual Reproduction 1 Yeast cells identify their mates by local cell signaling. 2 3 AP Biology Exchange of mating factors. Each cell type secretes a mating factor that binds to receptors on the other cell type. Mating. Binding of the factors to receptors induces changes in the cells that lead to their fusion. New a/ cell. The nucleus of the fused cell includes all the genes from the a and a cells. factor Receptor a Yeast cell, mating type a factor Yeast cell, mating type a a/ Long Distance Signaling Use of hormones Can affect many cells Protein or Steroid types AP Biology Signal Transduction Pathways Convert signals on a cell’s surface into cellular responses AP Biology 3 Phases of Signal Transduction EXTRACELLULAR FLUID 1 Reception Plasma membrane CYTOPLASM 2 Transduction 3 Response Receptor Activation of cellular response Relay molecules in a signal transduction pathway Signal molecule Figure 11.5 AP Biology Step One - Reception Reception occurs when a signal molecule (ligand) binds to a receptor protein. Ligand and receptor have a unique bonding AP Biology Step Two - Transduction Signal initiated by conformational change of receptor protein Signal is turned into a cellular response. cascades relay signals to target second messengers involved Multistep pathways can amplify a signal AP Biology Transduction by a phosphorylation cascade Signal molecule Receptor Activated relay molecule Inactive protein kinase 1 1 A relay molecule activates protein kinase 1. 2 Active protein kinase 1 transfers a phosphate from ATP to an inactive molecule of protein kinase 2, thus activating this second kinase. Active protein kinase 1 Inactive protein kinase 2 ATP ADP Pi PP Inactive ATP protein kinase ADP 3 5 Enzymes called protein phosphatases (PP) PP catalyze the removal of Pi the phosphate groups from the proteins, Inactive making them inactive protein and available for reuse. Figure 11.8 AP Biology 3 Active protein kinase 2 then catalyzes the phosphorylation (and activation) of protein kinase 3. P Active protein kinase 2 Active protein kinase 3 P 4 Finally, active protein kinase 3 phosphorylates a protein (pink) that brings about the cell’s response to the signal. ATP P ADP Pi PP Active protein Cellular response Benefits of a 2° messenger system signal 1 Activated adenylyl cyclase receptor protein 2 Not yet activated amplification 4 3 GTP amplification cAMP amplification 5 G protein protein kinase 6 amplification Amplification! enzyme Cascade multiplier! AP Biologyresponse! FAST 7 amplification VIDEO product Step Three - Response Cell signaling leads to regulation of cytoplasmic activities or gene expression AP Biology Regulating Gene Expression AP Biology Types of Receptors There are three main types of plasma membrane receptors: G-protein-linked Tyrosine kinases Ion channel Intracellular AP Biology G-protein-linked receptors Very common Results in a single pathway response AP Biology Receptor tyrosine kinases Multiple pathway response Signal-binding site Signal molecule Helix in the Membrane Signal molecule Tyrosines Tyr Tyr Tyr CYTOPLASM Receptor tyrosine kinase proteins (inactive monomers) Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Dimer Figure 11.7 Activated relay proteins Tyr Tyr Tyr Tyr Tyr Tyr 6 ATP Activated tyrosinekinase regions (unphosphorylated dimer) AP Biology 6 ADP P Tyr P Tyr P Tyr Tyr P Tyr P Tyr P Fully activated receptor tyrosine-kinase (phosphorylated dimer) P Tyr P Tyr P Tyr Tyr P Tyr P Tyr P Inactive relay proteins Cellular response 1 Cellular response 2 Ion Channel Receptors • When ligand binds, channel can open or close. Ex: neurotransmitters bind as ligands for Na+ ion channels AP Biology Intracellular Receptors Target protein is INSIDE the cell Must be hydrophobic molecule Hormone EXTRACELLULAR (testosterone) FLUID Why can the signal molecule meet its target INSIDE the cell? Receptor protein Plasma membrane Hormonereceptor complex 2 Testosterone binds to a receptor protein in the cytoplasm, activating it. NUCLEUS CYTOPLASM receptor complex enters the nucleus and binds to specific genes. 4 mRNA AP Biology hormone testosterone passes through the plasma membrane. 3 The hormone- DNA Figure 11.6 1 The steroid New protein The bound protein stimulates the transcription of the gene into mRNA. 5 The mRNA is translated into a specific protein. Evolutionary Significance Unicellular and multicellular cell communication have similarities Highly conserved mechanisms Bacteria secrete molecules to sense density of own population. Quorum Sensing TEDED Quorum Sensing AP Biology