STEM CELLSThe origin of all cells in a multicellular organism*The single cell becomes 2, then 4, then 8 then… as the cells divide they also specialize to make different tissues*This is a fluorescently stained developing organism showing the different cells in the organism-al of these arose form the original blastocyst. Some types of differentiated cells found in humans and other animals*Muscle cells-used to generate force for movement, pump fluids, etc.*Neural cells-Use for communication and signaling*Skin cells-Used to separate the organism from the environment and provide a selective barrierMesenchymal stem cells (MSCs)*Undifferentiated cells- can become anything*The progenitor cells for many tissues are MSCs-Can be derived from embryonic cell controversial-Can be derived from adult cells- not efficient and problematic*Extracellular signals are needed-Some tell the MSC’s what type of cell to turn into-Some tell the MSC’s to divide and make identical copies or self-renewImportant differences and similarities between stem cells and differentiated cells1. Both stem cells and differentiated cells have all the same genes. They differ in the regulation of those genes and express very different sets of genes2. Stem cells and differentiated cells can send and receive signals but their ability to d so changes as cells mature.3. Stem cells can divide and differentiated, maturing cells can still divide as they differentiate. Most fully mature cells no longer divide.Cell Signaling *First a cell receives an external signal in the form of a molecule-The signaling molecule binds to a receptor on the cell surface*Stage 2 is signal transduction-A series of chemical changes within the cell is triggered (FUCK HIM)Signal transduction*Often a series of protein chemical transformations*Two in particular that we will look at-addition of a phosphate group- carried out by a kinase protein-Removal of phosphate from a protein- carried out by a phosphatase protein Signal Transduction and stem cell self-renewalR= ReceptorTK1= Kinase 1TK2= Kinase 2TF= Transcription factorRNAp= RNA polymeraseSR=Self renewal ligandPO4= Phosphate added to
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