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Lecture 11

Lecture 11 - Cell Signalling Part 1 - February 14.docx

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BIOL 2021
Patricia Lakin- Thomas

February 14, 2013 Lecture 10: Chapter 15 – Cell Communications (Going to be Long as Hell) Most of the drugs being used affect signalling pathways General Principles of Signalling  Figure 15.1 – signalling pathways  Extracellular signal molecules  Receptor protein – signal binds to receptor = ligand  Intracellular signalling pathways  Effector proteins Receptors  Cell surface receptors – 15.3a o Binds to a hydrophilic signal molecule o Signal cannot get inside the cell – sends signal through signal bound receptor  Intracellular receptors – 15-3b o Can get inside the cell o Ligand is hydrophobic and small, crosses membrane o Often carried by a carrier protein inside the blood to be hydrophilic Signalling Distances  Contact dependant signalling – 15.4A o Signal has to be bound on the surface of cells o Only affects neighbor cells that are physically touching each other o Utilize membrane bound proteins  Paracrine Signalling – 15.4B o Secreted signals leave the cell and only act locally o Diffuse poorly or degrade rapidly o Target cells are nearby – membrane bound receptors o Special kind – autocrine:  Local but only affects the same cell (hence “auto”) – cell responds to own signal  Synaptic Signalling – 15.4C o Neural impulses o Long distance to another specific neuron at the synapse  Endocrine Signalling – 15.4 D o Cells secrete hormones and put it into the BLOODSTREAM o Signal is long distance to many other cells Speeds of Cellular Responses  Figure 15-6  Depends on target inside the cell  Very fast – responses of ion channels in an action potential [ms]  Fast – Change in movement (cell changes cytoskeleton to change direction; secretion; metabolism)[s – min]  Slow – change in gene expression  protein synthesis  cell growth division [min – hrs] Multiple Extracellular Signals  Figure 15.8  Different signals produce different responses in the same cell  Different receptors for each different signal  Acetylcholine – fig 15.9A (structure) o Response in heart muscle – Figure 15.9b  Causes a decrease in force and timing of contraction o Skeletal muscle – Figure 15.9B  Causes contraction o Secretory cells – Figure 15.9C  Causes secretion o Different signals because of different receptors and/or signalling pathways o Caused by developmental history Intracellular Receptors  Classification of receptors on Moodle  Ligands are hydrophobic signals – can go straight across PM  Receptor proteins are inside the cell  Nitric Oxide and Smooth Muscle – 15.12A (note this is “drawn wrong”) o In a blood vessel, if muscles relax  dilation (fig 15.12b) o Neuron will release acetylcholine – endothelial cell has receptor o Nitric oxide synthase is activated – makes NO o Diffuses to the muscle cells – binds to receptor (enzyme) called guanylyl cyclase o Creates cyclic GMP (cGMP) [phosphodiesterase)  causes rapid relaxation  more blood flow o Drugs: Nitroglycerine  Good for treating angina – blood vessel contraction in the heart o Drugs: Viagara  Inhibits cGMP phosphodiesterase in the penis  Increase in cGMP  Nuclear receptors – Figure 15. 3 (Ligands for nuclear receptors) o Steroid hormones o Cortisol sex hormones o Vitamin D o Bind to nuclear receptors = gene reg
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