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Bio 1510 - 9_1 - Bio – 1510 Basic Life Mechanisms Bio...

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Unformatted text preview: Bio – 1510 Basic Life Mechanisms Bio Fall 2008 Dr. Rasheeda Zafar Lecture # 9 Cell Communication Cell 1 Cell Communication Cell Communication between cells Communication Ligand The signaling molecule Receptor protein Receptor The molecule to which the signal binds May be on the plasma membrane or within the cell 2 Cell Signaling Cell 3 Cell Communication Cell Four basic mechanisms Four Direct contact Direct Paracrine signaling Paracrine Endocrine signaling Endocrine Synaptic signaling Synaptic 4 Cell Communication Cell Direct contact Direct Molecules on the surface of one cell are recognized by receptors on the adjacent cell Paracrine signaling Paracrine Signal released from a cell has an effect on neighboring cells 5 Cell Communication Cell Endocrine signaling Endocrine Hormones released from a cell affect other cells throughout the body Synaptic signaling Synaptic Nerve cells release the signal (neurotransmitter) which binds to receptors on nearby cells 6 Cell Communication Cell Signal Transduction Signal Cell response when ligand binds to receptor protein Events within the cell that occur in response to a signal Different cell types can respond differently to the same signal 7 Cell Communication Cell A cell’s response to a cell’s signal often involve signal activating or inactivating activating proteins proteins Phosphorylation Phosphorylation A common way to change the activity of protein Protein kinase Protein An enzyme that adds a phosphate to a protein Phosphatase Phosphatase An enzyme that removes a phosphate from a protein 8 Receptor Types Receptor Receptors can be defined by their location Receptors Intracellular receptor Intracellular Located within the cell Cell surface receptor or membrane receptor Cell Located on plasma membrane to bind a ligand outside the cell 9 Receptor Types Receptor Three subclasses of membrane receptors Three Channel linked receptors Channel Enzymatic receptors Enzymatic G protein-coupled receptor protein-coupled 10 Receptor Types Receptor Channel Linked Receptors Channel Ion channel that opens in response to a ligand ligand 11 Receptor Types Receptor Enzymatic Receptors Receptor is an enzyme that is activated by the ligand by 12 Receptor Types Receptor G protein-coupled receptor protein-coupled G-protein (bound to GTP) assists in G-protein transmitting the signal transmitting 13 Intracellular Receptors Intracellular Steroid hormones Steroid Have a nonpolar lipid-soluble structure Can cross the plasma membrane to a steroid receptor receptor Usually affect regulation of gene expression An inhibitor blocks the receptor from binding to An DNA until the hormone is present DNA 14 Intracellular Receptors Intracellular Steroid receptor has 3 functional domains functional Hormone-binding domain DNA binding domain Domain that interacts with coactivators to affect gene expression 15 Intracellular Receptors Intracellular 16 Receptor Kinases Receptor Receptor tyrosine kinases Membrane receptor When bound by a ligand, the receptor is activated by dimerization and autophosphorylation Activated receptor adds a phosphate to tyrosine on a response protein An example is the insulin receptor insulin 17 Receptor Kinases Receptor 18 Receptor Kinases Receptor Insulin receptor 19 Receptor Kinases Receptor Kinase cascade Kinase Series of protein kinases that phosphorylate each other in succession Amplifies the signal because a few signal molecules can elicit 20 Receptor Kinases Receptor Mitogen activated protein Mitogen (MAP) kinases (MAP) Avtivated by kinase cascade 21 G-Protein Coupled Receptors G-Protein G-protein G-protein Protein bound to GTP G-protein-coupled receptor (GPCRs) – Receptors bound to G proteins G-protein is a switch turned on by the receptor G-protein G-protein then activates an effector protein (usually an enzyme) 22 G-Protein Coupled Receptors G-Protein 23 G-Protein Coupled Receptors G-Protein The effector protein produces a second messenger. Second messenger generates the cellular response to the original signal Example– one common effector protein is adenylyl cyclase which produces cAMP as a second messenger. cAMP 2+ 2+ Other second messengers include inositol phosphates, 24 G-Protein Coupled Receptors G-Protein 25 Cell-to-Cell Interactions Cell-to-Cell Cells can identify each other by cell surface markers. surface Glycolipids are commonly used as tissue-specific Glycolipids markers Major histocompatibility complex (MHC) proteins are used by cells to distinguish “self” from “nonself” 26 Cell-to-Cell Interactions Cell-to-Cell Cell Junctions Cell Connection between cells within a tissue Connection Three major types Three Tight Junctions Tight Anchoring Junctions Anchoring Communicating junctions Communicating Gap junctions Gap In animal cells In Plasmodesmata Plasmodesmata In plant cells In 27 Cell-to-Cell Interactions Cell-to-Cell Tight Junctions Tight Create sheets of cells 28 Cell-to-Cell Interactions Cell-to-Cell Anchoring junctions Anchoring Connect the cytoskeletons Connect adjacent cells adjacent 29 Cell-to-Cell Interactions Cell-to-Cell Communicating Junctions Communicating Permit small molecules to pass between cells 30 Cell-to-Cell Interactions Cell-to-Cell 31 Cell-to-Cell Interactions Cell-to-Cell Gap junction Gap Animal Cells Animal Plasmodesmata Plasmodesmata Plant cells Plant 32 ...
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