Ch 11 Prokaryote and eukaryote have cellular communication Bacteria protozoa yeast are good at mass communication Biofilm plaque full of microorganisms to aggregate They can exploit resources have all kinds of activities without having stress when they aggregate in mass Most of the bacteria in biofilms sense the population of how many are there They sense how much of the local density is Aggregation is called quorum sensing how the bacteria sense the concentration of signals coming from outside They wait and see if all of them come before they start something A behavior is triggered based on the population Local signaling short distance signaling Most gap junctions plasmodesmata in cells where chemicals go back and forth Some also have cell recognition No contact but release chemicals that travel some distance Synaptic signaling nerve cells communicate the area between 2 nerve cells synapse Most growth factors communicate through paracrine signaling Telling the cells to grow Long distance signaling most hormones communicate this way Hormone released in brain but response could be somewhere else Endocrine signaling A particular pathway is followed by all types of signaling communication o Reception a protein binds to the receptor a series of reactions are released o Transduction relay molecules o Response whatever the signal molecule came to do is responded Signaling molecules are called Ligand Ligands bind to the receptor molecules but they re big so cant just enter the membrane 3 main receptor proteins Once the signal binds to the receptor there s a change and a pathway is triggered o GPCRs need to be activated Whenever a G Protein needs to be activated it uses GTP similar to ATP You re trying to target GPCRs to the host cell o RTKs this receptor to be active phosphate group is added Tyrosine amino acid is sitting in an inactive form until the signaling molecule attach to them forming a dimer and making them active This leads to the phosphorylation of tyrosine They tend to activate several transactions at a time While GPCRs only do one at a time o Ligand gated ion channel allowing ions to come in most neurotransmitters use this Intracellular receptors there are some receptors that are also inside the cell Some would have to have any small hydrophobic molecule to help them move inside the cell They have some response within nucleus or in cytoplasm they don t need help and can come directly into intracellular area Phosphatases help remove phosphate group Kinase help add them The point of it to have several different responses Most second messengers are non polar and small Example cAMP Its cyclic because the way it binds They also target when you keep cgmp active it keeps blood flow active to the penis how Viagra works ATP is transferred to cAMP by an enzyme look at the picture How is this pathway regulated How is amplification is done Each cell having same signal molecule can behave differently because of different sets of protein ligand To make sure signal is transferred efficiently scaffolding protein is used Apoptosis cell death important in eukaryote Some enzymes destroy cells and main one is Caspases they cut off all the protein
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