BIS104 Note4

BIS104 Note4 - Lecture 4 Bio Sci 104 Protein and Lipid...

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Lecture 4 1 Bio Sci 104 Winter 2010 Protein and Lipid Trafficking-I I. Overview A. Spatial organization. This is a central aspect of cell biology, and what distinguishes it as discipline from biochemistry. B. Membranous compartments separate cell from environment, and (in eukaryotes) partition the inside of cell into distinct organelles. C. How are eukaryotic membranous compartments created, maintained, and destroyed? Basically, how do things get where they should be? How do membrane proteins and lipids we discussed last lecture end up in the correct membranes? S ubcellular trafficking machinery ensures correct molecules target to correct compartments. We will discuss proteins, RNAs, and lipids. D. Important to note that the inside of Golgi and endoplasmic reticulum is topologically equivalent to extracellular environment . Proteins on inside of ER are equivalent to proteins on outside of cell. Also note that nuclear double bilayer is continuous with ER , also has ribosomes associated with it. E. Three distinct ways things get from one subcellular compartment (e.g. site of synthesis) to another (e.g. site of action): 1. transmembrane transport – transport of selective proteins from the cytocol into ER lumen or mitochondria, peroxisome etc occurs this way. Transmembrane transport into ER is a process by which membrane proteins and secreted proteins (synthesized on cytoplasmic surface of ER) pass through ER membrane into ER lumen 2. vesicular transport . The lumen of the ER is not the final destination for most proteins or lipids. Some proteins end up permanently residing in PM, some are released into extracellular environment, some target to lysosomes. 3. gated transport - method by which RNA leaves nucleus and proteins enter. Distinct from (1) in that selective pores/translocators in nuclear membrane control this process, allowing free diffusion of some molecules and regulated gating of others. F. Protein trafficking is regulated by signal sequences - spec ia l ized str ings of am
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Lecture 4 2 1. Typically a net-like complex of branching tubules, sacs, and vesicles extending through much of the cytosol, probably forming a continuous or near-continuous sheet enclosing an internal space called the ER lumen. Over half of the membrane in a typical animal cell is in ER. 2. The lumen typically may represent
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BIS104 Note4 - Lecture 4 Bio Sci 104 Protein and Lipid...

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