Three stages of the Signal- Transduction Pathway

Transcription

1 Typical Signal Transduction Pathway Typical Signal Transduction Pathway Endocrine & Cell Communication Part III: Hormonal Communication Enduring Understanding 3.D Cells communicate by generating, transmitting and receiving chemical signals. EK 3D2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling c. Signals released by one cell type can travel long distances to target cells of another cell types. 1. Endocrine signals are produced by endocrine cells that release signaling s, which are specific and can travel long distances through the blood to reach all parts of the body. Ligand = Chemical Messenger Three major classes of s function as s in vertebrates (ligands) Polypeptides (proteins and peptides) Amines derived from amino acids Steroid s Phase 1: Reception The target cell detects the ligand Membrane proteins G-protein linked receptors Ion channel receptors Tyrosine Kinase Intracellular receptor Steroid receptors 2 5 The Process of Communication: Signal-Transduction Pathway Ligands Type of Receptor : G-protein linked Three stages of the Signal- Transduction Pathway 1. reception 2. transduction 3. response LIGAND: a that binds to a larger 1

2 Type of Receptor: Ion Channel Name three types of receptors in the signal transduction pathway G-protein-linked receptors Ion channel receptors Intracellular receptors Transduction Binding changes the receptor protein. Can set off a cascade reaction Type of Receptor: Intracellular Receptor Action of G-Protein Linked Receptor Response Set any of a variety of cell activities in motion. Activation of an enzyme Rearrangement of cytoskeleton features Activation of a specific gene 2

3 Recap Which Is A Receptor Through Which Ions Would Pass? EXTRAULAR FLUID 1 Reception Receptor Plasma membrane CYTOPLASM Signaling Recap Types of Receptors Which Of These Acts As A Second Messenger? EXTRAULAR FLUID 1 Reception Receptor Plasma membrane 2 Transduction CYTOPLASM Relay s in a signal transduction pathway + Signaling 23 Recap Which is the receptor? G-Protein? Ligand? Water-soluble (hydrophilic) Polypeptides Lipid-soluble (hydrophobic) Steroids EXTRAULAR FLUID Plasma membrane CYTOPLASM 1 Reception 2 Transduction 3 Response Receptor Relay s in a signal transduction pathway Activation of cellular response 0.8 nm Insulin Amines Cortisol Signaling Epinephrine Thyroxine 3

4 Cellular Response Pathways Water- and lipid-soluble s differ in their paths through a body Water-soluble s are secreted by exocytosis, travel freely in the bloodstream, and bind to cellsurface receptors Lipid-soluble s diffuse across cell membranes, travel in the bloodstream bound to transport proteins, and diffuse through the membrane of target cells Pathway for Water-Soluble Hormones Binding of a to its receptor initiates a signal transduction pathway leading to responses in the cytoplasm, enzyme activation, or a change in gene expression Pathway for Lipid-Soluble Hormones The response to a lipid-soluble is usually a change in gene expression Steroids, thyroid s, and the hormonal form of vitamin D enter target cells and bind to protein receptors in the cytoplasm or nucleus Protein-receptor complexes then act as transcription factors in the nucleus, regulating transcription of specific genes SECRETORY Pathway for Water-Soluble Hormones Pathway for Lipid-Soluble Hormones Lipidsoluble Watersoluble VIA BLOOD Signal receptor Transport protein TARGET Signal receptor (a) NUCLEUS (b) SECRETORY Specific Example Steroid Hormone Example: Testosterone Lipidsoluble Watersoluble VIA BLOOD Signal receptor Transport protein Notice the presence of the second messenger TARGET OR Signal receptor Cytoplasmic response Gene regulation NUCLEUS (a) Cytoplasmic response (b) Gene regulation Click here to view the animation 4

5 Compare protein and steroid s by completing this T chart Characteristic Protein Hormone Steroid Hormone Speed of response Rapid response, cascade Response is slower, gene expression Primary bio composition Amino acid cholesterol Method of leaving secretory cell Exocytosis diffusion Location of receptor Membrane bound Intracellular Example Epinephrine Testosterone Model Steroid Hormone Action using the Testosterone Manipulative Multiple Effects of Hormones The same may have different effects on target cells that have Different receptors for the Different signal transduction pathways Same receptors but different intracellular proteins (not shown) Different cellular responses Different receptors Different cellular responses Epinephrine Epinephrine Epinephrine β receptor β receptor α receptor Glycogen deposits Glycogen breaks down and glucose is released from cell. Vessel dilates. Vessel constricts. 38 (a) Liver cell (b) Skeletal muscle blood vessel (c) Intestinal blood vessel Compare protein and steroid s by completing this T chart Characteristic Protein Hormone Steroid Hormone Speed of response Primary bio composition Method of leaving secretory cell Location of receptor Example Multiple Effects of Hormones The epinephrine has multiple effects in mediating the body s response to short-term stress Epinephrine binds to receptors on the plasma membrane of liver cells This triggers the release of messenger s that activate enzymes and result in the release of glucose into the bloodstream Did you know One reason that kittens sleep so much is because a growth is released only during sleep. The levels of two stress s, cortisol and epinephrine which suppress the body's immune system, will actually drop after a dose of laughter. Chocolate is associated with the release of serotonin, the that makes you feel relaxed, calm, and happy. So are hugs. 39 5

6 Created by: Debra Richards Coordinator of Secondary Science Programs Bryan ISD Bryan, TX 6