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BIOL 1105 - week 4 notes

by: Words'nNotes

BIOL 1105 - week 4 notes BIOL 1105

Virginia Tech

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About this Document

Covers: cell communication, signaling types, and receptor types
Principles of Biology
Eric P. Hogan
Class Notes
Biology, Cellular, communication, receptors, signaling
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This 4 page Class Notes was uploaded by Words'nNotes on Sunday September 11, 2016. The Class Notes belongs to BIOL 1105 at Virginia Polytechnic Institute and State University taught by Eric P. Hogan in Fall 2016 2016. Since its upload, it has received 4 views. For similar materials see Principles of Biology in Biology at Virginia Polytechnic Institute and State University.


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Date Created: 09/11/16
Cell communication Cell communication and cell signaling are two terms for the same thing Cell communication involves a signaling and a target cell  Signaling cell creates and release the signal (called a ligand)  Target cells use receptor proteins that bond with the ligand, the cell then responds Types of communication: The types are classified by the distance required for the signal to travel before reaching its destination Direct contact is between two touching cells, gap junction (small tubes between the two cells) allow for signals to travel, used where cells must function together, the fastest form of communication, commonly used to coordinate such as with heart muscles Paracrine Signaling is where signals are diffused a short distance to other nearby cells, local and somewhat fast, this only lasts a short while as the nearby cells quickly absorb the signal protein, used in immune system Autocrine Signaling is similar to Paracrine Signaling in that a cell releases a signal but then the same cell is the intended target cell, signaling itself, somewhat fast, used in immune system Endocrine signaling is where signals are secreted into the bloodstream and must travel a long distance to reach their target, slow but long lasting as it takes longer for the signals to be absorbed, in this process signals are called hormones Synaptic signaling is used only by nerve cells, has a long and short distance variety, the long distance takes place along the elongated cell membrane where it is released at the end to a nearby cell, fast but long distance. Signal chemistry and Receptor location Cell surface detectors detect peptides proteins and neurotransmitters as they can’t cross the cell membrane, surface detectors have three parts: an extracellular domain for binding to the signal, a transmembrane domain that holds it in place, and cytosolic domain that leads to a transduction pathway Transduction pathways include several steps of activation to a cellular response Intracellular receptors are located inside the cell and bond to hydrophobic signals (ligands) as they can pass through the cellular membrane, the receptors then activate a signal transduction pathway, the pathway has fewer steps than Surface receptors, used by steroids Steroid Receptors control gene expression Steroids are involved in endocrine signaling Steroids are often transcription factors Surface receptors tend to have more steps in in their transduction pathways than intracellular receptors There is more than one type of surface receptor: ion channels, enzymes, and GPCRs (g protein couple receptors) The different receptors have different pathways to produce a response in the cell: effector proteins, molecular switches, and second messengers Then response proteins are activated and respond Classes of cell surface receptors 1. Channel linked receptors are gated ion channels, used in nerve cells 2. Enzymatic receptors are activated when the signal binds to them and activates their cytosolic domain, only active when the signal is bound to the receptor Molecular switches Phosphorylation: the process by which a phosphate can be added to a protein and switches it on or off dependent, kinase add the phosphate while phosphatase removes it, whether adding a phosphate turns a protein on or switches it off is variable RTK deals with growth factor, it is the most well understood intracellular pathways, it has many steps to cause a cellular response including activation of RAS RAS: when bound to GTP the protein is on and it is off when bound to GDP, defects in this system lead to RAS staying constantly on and causes a large majority of cancers. Signal pathways can amplify the signal as an activator protein can activate more than one of the next step in the process and that step can activate more than one of the next step, and so on. A class of protein Receptor G-protein coupled receptors, can detect neurotransmitters odors tastes photons endocrine hormones and growth factors, have a conserved multi-pass membrane domain and can interact with the G protein on the interior of the cell Most signal pathways are reversible (shut down when no signal is present) Signals only last a limited time before they are destroyed or absorbed as signal production stops Components in the pathways then deactivate


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