BCOR 103 1st Edition Lecture 13Outline of Last Lecture I. Membrane/Secretory PathwayII. Protein TranslocationOutline of Current Lecture I. Sorting of ProteinsII. Uptake of Materials in the Plasma MembraneCurrent LectureThe Golgi complex is largely responsible for getting proteins to their final destination. The four major parts of protein sorting are Golgi localization, ER-Golgi exchange, lysosomal targeting, andsecretion. The Golgi localizes the proteins that are meant to remain in the Golgi. Occasionally proteins within the ER will be needed in the Golgi. When this happens the protein is tagged with a “KDEL” which allows the protein to dock in the Golgi, but then ultimately be returned to the ER. Some proteins need to be transported to a lysosome. This process happens in a series of steps. First, the lysosomal enzymes are inserted through the membrane of the ER and are glycosylated and sent to the Golgi. Next the cis Golgi the proteins are recognized and a sugar group is added. This sugar group is called a “Mannose-6-Phosphate” tag. After the protein arrives at the Trans Golgi it will sent and received by the receptor for Mannose-6-Phosphate. It is then put into a vesicle and transported through the cytosol to the lysosome. The last type of sorting that occurs is secretion. Secretion occurs from the Trans Golgi Network (TGN) in two pathways, constitutive and regulated. The constitutive pathway carries out the ongoing deliveryproteins to the plasma membrane for export. The regulated pathway has a series of steps to secrete a protein. The specific amino acid sequence on the protein binds to a “granin” protein that is contained the Cis Golgi. Once it reaches the Trans Golgi the hydrogen and calcium withinthe Trans Golgi causes the protein to become insoluble. Specific receptors bind the protein granule and then a vesicle buds off from the Golgi and travels to the plasma membrane. Uptake of materials at the plasma membrane is comprised of three processes. The first is phagocytosis or “cell eating.” In this process the cell membrane slowly engulfs smaller organisms or material. The second is pinocytosis or “cell drinking.” This process is the nonspecific uptake of an extracellular fluid into the cell. The last process is receptor mediated endocytosis. There are four steps involved. First, the material is bound to an integral These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.membrane receptor. Next the receptor and material pinch off and enter the cell. This vesicle fuses with endosomes and the acidification leads to the release of the
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