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Chapter 11

by: Sophia Notetaker

Chapter 11 BIOC 0170

Sophia Notetaker
GPA 3.5

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Chapter 11, Biology
Foundation of Biology I
Barbara Barnhart
Class Notes
Biology, Chapter 11
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This 8 page Class Notes was uploaded by Sophia Notetaker on Wednesday February 17, 2016. The Class Notes belongs to BIOC 0170 at University of Pittsburgh taught by Barbara Barnhart in Spring 2016. Since its upload, it has received 14 views. For similar materials see Foundation of Biology I in Biology at University of Pittsburgh.


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Date Created: 02/17/16
Chapter 11 – Cell Communication I. Signal Transduction Pathway a. Stimulus triggers series of steps within cell resulting in specific cellular response i. It going to cell to do something. It goes to a pathway b. Signal can be local i. Direct Contact 1. cell junctions a. Occurs in animals and plants b. Chemical signals pass through junctions c. Connects cytoplasm and adjacent cells d. Gap junctions and plasmodesmata 2. cell-cell recognition a. Occurs in animals’ cells b. Communicate through surface molecules i. Glycoproteins c. Important in embryo development and immune response i. Important this part 3. Secretion 1 Ch. 11 – Cell Communication a. Messengers that travel short distances secreted by a signaling cell b. paracrine signaling i. Local regulator molecule secreted by signaling cell ii. Secreted in extracellular fluid iii. Local regulator influences nearby target cell ( can be several) iv. Grown factors use this c. synaptic signaling i. Electrical signal along nerve cell signals release of neurotransmitters ii. Neurotransmitter diffuse across synapse c. Signal can be long distance i. (Under Signal Transduction Pathway) ii. Nerve Cells 1. Electrical signals travels length of nerve cell 2. Instead of signaling release of neurotransmitter, remains an electrical signal 3. Electrical signal travels through a series of nerve cell d. Animals Figure 1 With note c i. (Signal can be long distance) ii. Endocrine signaling (hormones) iii. Hormones released iv. Hormone travel through circulatory system v. Target cells recognize and respond to hormones vi. Plants 1. Hormones can travel in vessels 2. Hormones can travel by diffusion through air as a gas II. Three Stages of Cell Signaling 2 Ch. 11 – Cell Communication A. Reception a. Signal molecule (ligand) complementary in shape to specific site on receptor i. Similar to active site and substrate) b. Signal molecules binds to receptor protein (usually a plasma membrane protein) c. Receptor protein changes shape i. Conformational change ii. Activates receptor d. Three types of membrane receptors i. 1. G-protein-coupled receptor (GPCR) - membrane protein) 1. Protein with guanine nucleotide (GDP) bound to it 2. Found on cytoplasmic side of plasma membrane 3. When activated receptor binds to G-protein which also becomes activated a. GTP displaces GDP 4. G-Proteins dissociated from receptor, dliffuses along membrane and bind to enzyme – triggers cellular response ii. 2. Receptor tyrosine kinase (RTK’s) 1. Membrane receptors that attach phosphate to tyrosine 2. Triggers more than one cellular response at same time 3. Tyrosine start out as monomers 3 Ch. 11 – Cell Communication 4. Signaling molecule (ligand) binds causing 2 receptors tyrosine Kinases to form a dimer 5. Dimerization activates tyrosine kinase region causing phosphate to bind to tyrosine 6. Relay proteins bind to phosphorylated tyrosine 7. Cause cellular response iii. 3. Ion channel receptor 1. Acts like a gate 2. Signal molecule binds to receptor 3. Causes gate to open to allow specific ions (Na+ and Ca ) to flow through channel 4. Causes change in concentration which leans to cellular response 5. When signaling molecule dissociates, gates closes 6. If things malfunction is can lead to cancer 7. Is the channel isn’t working right, there nervous system can be bad e. Intracellular Receptors (Internal) i. Insoluble (hydrophobic) and small ii. Hydrophobic signal molecule can cross membrane iii. Binds to receptor protein 4 Ch. 11 – Cell Communication iv. Can cross the membrane because they are small and hydrophobic and binds with the tail B. Transduction a. Multistep pathway b. Relays signal from receptor to target molecule in cell c. Receptor protein activates another molecule, which activates another molecule and so on – relay molecules d. Relay molecules activated until final protein is reached to cause cell response e. Proteins activated by conformational change f. Phosphorylation causes conformational change i. Protein kinase (enzyme) transfer inorganic phosphate from ATP to next protein in pathway - hosphlaylate – adding a phosphate ii. Protein phosphatases (enzyme) removes inorganic phosphate from protein – dephosphorylation – taking a phosphate away) iii. We add a phosphate and activate it. g. Second Messengers i. Small, non-protein water-soluble molecules or ions ii. Relay signals received from outside iii. Can spread easily to all regions of cell iv. Not Proteins v. Two mainly used 2 ndmessengers 5 Ch. 11 – Cell Communication 1. cAMP – cyclic adenosine monophosphate a. Adenylyl cyclase (enzyme) converts ATP to cAMP in response to extracellular signal b. Usually part of G-protein system i. Membrane receptor protein activates adenylyl cyclase ii. Adenylyl cyclase makes cAMP iii. Kinase adds inorganic phosphate to other protein which cause cellular response iv. Look at the figure below 2. Calcium a. Involved in muscle cell contraction cell division and many others b. Pathway complicated (don't need to know) c. Involves 2 other messenger i. Inositol triphosphate (IP3) ii. Diacyglycerol (DAG) C. Response a. Regulation of one or more cellular activities resulting from original extracellular signal Figure 2 For note 1 b. Can occur in nucleus or the cytoplasm c. Responses can: i. Regulate protein synthesis 1. By turning genes on or off that makes enzymes 2. Transcription factor 3. Malfunction cause cancer ii. Regulate protein activity 6 Ch. 11 – Cell Communication 1. Turning enzyme activity on or off (Note C.) To i. activate it add a phosphate iii. Regulate other cellular attributes 1. Example: Mating of yeast cells III. Fine Tuning of Signals A. Amplification a. Each step activates a great number of products b. One signal molecule outside cell can result in release of millions of final response molecules c. Different types of cell responds to different signals B. Specificity a. Different cells contain different protein therefore different types of cell respond to different signals i. Cells ignore signals that don’t affect them ii. Same signal can trigger different response in different cell iii. Ex Epinnephhrine  Heart  Increase heart rate iv. Epinephrine LiverBreakdown glucose tends to be ignore C. Efficiency a. Scaffolding Proteins i. Large relay protein to which several other relay proteins are simultaneously attached to increase efficiently of signal transduction ii. Similar to a coordinator 7 Ch. 11 – Cell Communication D. Termination a. Cells contently communicate b. Cellular response is constantly being turned on and off c. The key to this is the reversibility of changes caused by the signal d. Binding o the signal to receptor proteins causes a conformational change – stares the cascade e. To stop the cascades, the signal is released from the receptor proteins in returns to original shape 8 Ch. 11 – Cell Communication


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