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Lec 1 - Prof Harris.pdf

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Maurice Ringuette

Lec 1 - Prof Harris. October 25, 20138:21 PM 2 linear polypeptides are coming together to fomr a dimer non covalently. Important question and is relevant to disease. Because when cells that paly a normal role in the body are the ones which goes berserk when we get diesases BIO230 Page 1 BIO230 Page 2 BIO230 Page 3 --> PM surrounds the other surface of the cell. Interface between the internal and external environment. Nice example: epithelial cell connected to another epithelial cell. These cells coats our gut. There are specific ends in the which faces the lumen of the gut which allows the cell to collect nutrients (pink). There are different molecular properties on the other side of the cell. Neurons: have two diff. main regions. Allows the neuron to collect signals from the dendrites and send it to the brain. To send neuro signal throughout the body How is the PM organization controlled? This is through membrane trafficking. Inside: white is cytosol Grey particles are membrane bound compartments. Small ones are vesicles The big one is the Golgi apparatus é ER The black lines are also membranes and inside these membrane there is a separate aqueous environment. So there are different pathways to bring in and out membrane material to and from the PM. Endocytic pathway: what comes in Biosynthetic secretory pathway: brings out ER : proteins are been made. They can be transported to the PM Extracellular and then taken to the lysosomes. Where proteins are been broken down. There are several basic principles to the trafficking routes.: space these regoins that are been marked has the potential of There's a flux of proteins from where proteins are to be made , used and broken down. There are trafficking system which are clearly defines. Polarized trafficking routes because all lines of the material is directed in one way. There arent simply single one way routes. There are also sorting stations. BIO230 Page 4 Protein trafficking routes Sorting Stations Membrane compaortments are coming from different sites and joining one site. This one site sends out materials to different end points. Things are coming from one place and goes to a different place of the cell. BIO230 Page 5 Retrieval Mechanisms and Genral Balance Among Routes The cargfo needs to be maintained in the overall cell. Endocytosis have to match exocytosis or else the cell is going to shrink or grow in size. The golgi has a place to take things and receive things. Constitutive: the cell is basically pumping things out from the cell continuously. It makig things from the ER to the golgi, making new secreted materials (blue) membrane lipids, proteins and these are constantly taking things to the membrane to resupply. The other materials are breaking down and these are resupplying them. Regulated secretion: the cell will make a store of vesicles containing specific cargo. Its only want to send it in a specific situation: eg: sending nerve impluses. Immune response. These vesicles are waiting for the signal and the signal comes along and activates the signal. BIO230 Page 6 Regardless of constitute or regulatory the mechainsm of going thorugh is kind of similar: The mechanism of these pathways: Cargo concetration and Retrieval of the transport machinery back into the system. In the golgi the cargo is not that concentrated --> it buds off to a immature secretory vesicle --> it has golgi components attached to it --> and recycles the golgi materials back to the golgi so the golgi maintains its size --> it becomes a mature secretory vesicle that can be secreted and released in the contrated forms of cargo. And releases the cargo. Concetrated cargo maintains the balance of the system A cargo just about when its about to be secreted from the surface of the cell. Conc cargo is the black blob. Lumen of the cargo. And the extracellular space. Seperating the two aquesous environements are membranes. The dark lines the outer plasma membrane. The vesicle will dock with the PM --> but there is a membrane as a barrier --> the membranes will fuse --> and recoil back and now Cargo cannot leave the cargo can be released to the extracellular space because membrane is blocking BIO230 Page 7 Mast cell: functions in immune response. When there is a pathogen I the system it releases histamin so it can attach the prey. Unstimulated state: vesicles are packed with histamin. Upon extra cellilar stimulatn formed in repsonse to the pathogen the vesicles fuses with the PM and release the histamin into the environement. Changes the environemetn and allowes other cells to come in and attack the prey easily Exocytosis can fill the membrane Which the bacteria A: Cell division. This is a Cell at a late stage of division. A single cell becomes two daughter cells and There is a huge need for a new PM in Fills up between the cells. B: immune cells takes the bacterium as phagocytosis. It takes a huge part of the PM with it. So exocytosis can resupply the PM C: Wound: physical lose of PM. So it is replaced by exocytosis. BIO230 Page 8 Endocytosis. Endocytic apthways conuter balance the secretory pathways. Perfomrs specific functions as well The PM starts to bend in and eventually the two lipid bilayers fuse and the vesicle pinches off into the cytosol. Once the vesicle has been endocytosed into the PM it has some choices to make. BIO230 Page 9 The endocytosis vesicle comes in Can go to the early endosomes which is a sorting station, and from there it can go to lysosome to be degraded, or to be recycled. Or to trasncytosis to another part of the cell. SORTING STATION Example of where cells use endocytosis: to collect cholesterol in the blood stream LDL - low density lipo proteins are floating around in the blood.--> LDL receptors bind to LDL--> recruit them to the sites with membranes bends in and pulls in the PM> puls the LDL with it--> its endocytosed- -> and sent to early endosomes to sort. LDL is released from the receptors and its receptors are used to send LDL and at this point it is released and it gets sent to lysosome. The lysosome degrades all the protein and releases choelsterol so it dan be released into the cell. BIO230 Page 10 The immune cell can pull the bacterium into the cell. And what is the machinery that is used? BIO230 Page 11 Fusion Exocytosis: appears as a fusion. Look at the PM> the contents at the vesicle to be transported the first two membranes has to fuse. The grey material is the cytosol. There is three aquesou membranes other than the cytosol . Cytosol . Lumen of the vesicle Extracellular space Critical think to keep track of: what happens to the lumen of the vesicle in contrast to the cytosol. The lumen of the vesicle becomes continuous with the extracellular space During exocytosis the lumens are readying itself to the become the extracellular environment. Endocytosis: what was the extracelular space is now in the lumen. It is in the opposite membrane configuration, and the invagination mmebrane is bending and the membrnae is invagination into the large cytosolic space. BIO230 Page 12 Little hard to understand: Budding of cytosolic particles into the Good way for cells to destroy contents lumen of the vesicel. It happens in the late endosomes to go onto the lysosomes. In the late endosomes there are membrane bound compartments inside the endosome and they are white colored Budding so they were derived from the cytosol. Membrane bound compartments inside the endosome. Big chunks of the cytosol are picked upand drawn into the endosome so they can be destroyed in lysosome. Multivesiclualr body: b
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