The Big Picture What are cells There are many ways to answer that Complex living systems Bats of protein that make more bags of proteins e g ability to independently reproduce Prokaryotic do not have a nucleus whereas eukaryotic do How do cells know what to do where to go etc Use stem cells as a model to discuss the answers to some of the questions What is a stem cell Stem cells have the remarkable potential to develop into many different cell types in the body during early life and growth In addition in many tissues that serve as a sort of internal repair system dividing essentially w o limit to replenish other cells as long as the person animal is still alive When a stem cell divides each new cell has the potential either to remain a stem cell or become another type of cell with a more specialized function such as muscle cells a red blood cell or a brain cell A cell type in which its job is to divide to make more cells or differentiate into cells with specialized functions e g heart blood liver etc Yeast amoeba are eukaryotic because they have a nucleus single celled organisms Stem cells CAN undergo cell division Can become many different types of cells e g have the potential to differentiate into cells w different functions stem cells make more cells differentiate into a specific cell type repairs adult bodies contain stem cells cannot duplicate once it s a specified cell terminally Differentiated cells Cannot undergo cell division Cannot differentiate any further perform spec functions in the body e g muscle cells or neurons or bone cells does a specific function different cell types are different because they express different genes multipotent blood stem cell differentiation red blood cell differentiated cells cannot duplicate because they don t receive signals if they do cancer stem cell to differentiated cell fertilized egg fetus how does this happen How do cells know which cell type to turn into OUTSIDE OF CELl receptor sits on cell surface O2 water phospholipids INSIDE OF CELL note make checklist of stem vs differentiated We can place stem cells into different categories depending on their differentiation potential or their potency the potency of a cell specifies its differentiation potential or potential to differentiate into diff cell types totipotency is the ability of a single cell to divide and produce All the differentiated cells in an organism including extra embryonic tissues pluripotent stem cells can give rise to any fetal or adult cell type however alone they cannot develop into a fetal or adult animal because they lack the potential to contribute to extra embryonic tissue such as the placenta e g inner mass cells inside a blastocyst week old fetus multipotent progenitor cells have the potential to give rise to cells from multiple but limited number of lineages unipotent are differentiated cells Oct4 receptor to a stem cell tumors are heterogeneous in a fetus totipotent early embryo pluripotent inner cell mass stem cellz what s the same between stem cells and differentiated cells their DNA FOR MOST STEM CELL TYPES when differentiation occurs the total DNA content does not change different types of stem cells embryonic stem cells ESC E G inner cell mass of blastocyst adult stem cells e g bone marrow needed for tissue repair what are so e other areas of the body where constant cell renewal is happening and where thee might be stem cells induced pluripotent stem cells iPS cells induced pluripotent system cells are adult cells that have been genetically reprogrammed to an embryonic stem cell like state by being forced to express genes and factors important for maintaining the defined properties of embryonic stem cell have to kill embryonic stem cell in order to use not hard to induce embryonic to be pluripotent hard to induce then to be liver cells real hypothetical transduction pathways Cell surface receptors receiving physicals signalling component Kinases Phosphatases transcription factors if stem cells and differentiated cells have the same Dna content then how do you get such diff types of cells with diff capabilities gene expression expression of diff genes leads to diff proteins diff receptors diff function All somatic cells have the SAME DNA But express different set of genes different cells differentiate or go through cell division somatic cells body cells not sex cells All cells should have the same number of genes every cell has the same genes no matter stem or differentiated transcription DNA gene RNA polymerase mRNA messenger ribosome protein mRNA can only be expressed in genes with the DNA stem cells only express oct4 cells receive an array of signals that tell them what to do survive grow and divide differentiate die apoptotic cell sometimes pathways get broken and cells that are told to die don t bad things necrosis cells die and so do all the cells around them catastrophic the same signal can be received by the same receptor but depending on the cell type the signal may affect different outcomes cytostolic signaling need things to relay signal from molecules effector molecules do other than gene expression pathways contain multiple components transcription factor screws gene expressions but not ion channel cell yes signal receptor receives signal receptor activates protein kinases kinases activate transcription factors transcription factors mark genes for expression RTK pathway aka mapk pathway Hypothetical simplified Transduction Pathway MAPK Mitogen Activated Protein Kinase Self Renewal Pathway activated by signal binding event Growth factor signals receptor RTK Receptor Tyrosine Kinase Kinase domains phosphorylate each other autophosphorylation Phosphorylate take from Adenosine Triphosphate ATP stick onto a proteinr Dimerization of receptor occurs upon signal binding Phosphorylation Change in the chemistry of a protein Turns on and off the protein TFa not phosphorylated cannot go into the nucleus Phosphorylation causes the chemistry of the molecule to change Activation deactivation differential binding characteristics etc Proteins structure function Two types of kinase Serine Threonine Signaling pathways can be regulated at every step Single cell molecule must have activated the thingamabober and left must dephosphorylate proteins to shut them down IF you have signal cells that phosphorylate whoever dafuq they want nothing good comes out of it Transcriptional level Controls level of mRNA Translational level COntrols how often the mRNA is