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Biology Lecture 15 - Exam 3

by: Devin Mart

Biology Lecture 15 - Exam 3 BIO 121 A

Marketplace > Missouri State University > Biology > BIO 121 A > Biology Lecture 15 Exam 3
Devin Mart
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Cell Communication
General Biology
Dr. Durham
Class Notes
Biology 120 - General Biology
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This 2 page Class Notes was uploaded by Devin Mart on Friday March 25, 2016. The Class Notes belongs to BIO 121 A at Missouri State University taught by Dr. Durham in Spring 2016. Since its upload, it has received 8 views. For similar materials see General Biology in Biology at Missouri State University.


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Date Created: 03/25/16
  Mart 1  Lecture 15: Cell Communication    ● Cellular communication is essential for both multi and unicellular organisms.  ○ Biologists have discovered some universal mechanisms of cellular regulation,  involving the same small set of cell­signaling mechanisms.  ■ Signals: chemical, electromagnetic, and mechanical.  ○ Signal­transduction pathway ​ is the process by which a signal on a cell’s surface is  converted into a specific cellular response.  ○ Paracrine signaling ​is a form of cell to cell communication in which a cell  produces a signal to induce changes in nearby cells, altering the behavior or  differentiation of those cells.  ○ Synaptic signaling ​only occurs between cells with thsynapse​.  ○ Hormones​  are a regulatory substance produced in an organism and transported in  tissue fluids such as blood or sap to stimulate specific cells or tissues into action.  ■ Cells communicate by ​ direct contac.  ● The three stages of cell signaling are reception, transduction, and response.  ○ Reception​  is the process of a chemical signal binding to a cellular protein,  typically at the cell’s surface.  ○ In ​transduction, binding leads to a change in the receptor that triggers a series of  changes along a signal transduction pathway.  ○ In ​response, the transduced signal triggers a specific cellular activity.  ○ A signal molecules (ligand) binds specifically to a receptor protein causing the  protein to change shape ­ activation.  ■ Most signal receptors are plasma membrane proteins which are often  water­soluble.  ○ Three major types of receptors: G­protein­linked receptors tyrosine­kinase  receptors, and ion­channel receptors.  ○ The G ​ protein ​cts as an on­off switch.  ■ When a GDP is bound it is inactive, whereas when a GTP is bound it is  active.  ○ Tyrosine­kinase receptors ​are used to regulate and coordinate many activities and  trigger several signal pathways at once.  ■ Tyrosine kinase transfers phosphate group from ATP to tyrosine on a  substrate.  ○ Ligand­gated ion channels ​ are protein pores that open or close in response to a  chemical signal.  ■ This is a very important aspect in the nervous system.  ● Multistep pathways greatly amplify the signal with a large cellular response.  ○ Pathways relay signals from receptors to cellular responses.    Mart 2  ○ Protein phosphorylation ​is a post­translational modification of proteins in which  an amino acid residue is phosphorylated by a protein kinase by the addition of a  covalently bound phosphate group.  ■ Protein kinases regulate protein activity, phosphorylation cascade,  inactive to active form, and phosphatases.  ● Many signaling pathways involve small, non protein, water­soluble molecules or ions,  called​econd messengers.​  ○ cAMP ​ (adenylate cyclase) converts ATP to cAMP, activates protein kinase.  ○ Calcium r egulates many functions of the cell.  ● In response to a signal, a cell may regulate activities in the cytoplasm or transcription in  the nucleus.  ○ Signaling pathways are used to amplify response to signal and contribute to  specificity of a response.  ○ Various types of cells may receive same signal but produce very different  responses.  ○ Different kinds of cells have different collections of proteins.  ○ Scaffolding proteins physically links signal pathways, and enhances speed and  accuracy of signal transfer between cells.  ○ Inherited disorder, Wiskott­Aldrich syndrome (WAS), is due to the absence of a  single relay protein.  ○ Activated signals must be inactivated by appropriate enzymes to prepare the cell  for a fresh signal. 


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