Biol Exam II

Biol Exam II - Biol Exam II Readings Sept 11th Protein...

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Biol Exam II Readings Sept 11 th Protein trafficking I (Chpt 15; pp 497-529) most organelles are formed from preexisting ones, which grow and divide 15-1 Cytosol – contains many metabolic pathways, protein synthesis ER – synthesis of most lipids, synthesis of proteins for distribution Golgi – modification, sorting, and packaging of proteins and lipids for secretion or delivery Lysosomes – intracellular degradation Endosomes – sorting of endocytosed material Mitochondria – ATP synthesis by oxidative phosphorylation Chloroplasts – ATP synthesis and carbon fixation by photosynthesis Peroxisomes – oxidation of toxic molecules Organelles purified by differential centrifugation synthesis of virtually all proteins in cell begins on ribosomes in the cytosol. Fate of protein depends on its primary sequence which may contain a sorting signal that directs the protein to the organelle in which it is required. Without a sorting signal the protein will remain in the cytosol 3 Mechanisms in which proteins are imported into Organelles through their membranes 1. Proteins moving form cytosol into nucleus are transported through the nuclear pores that penetrate the inner and outer nuclear membranes. Pores function as selective gates that activel y transport specific macromolecules but also allow free diffusion of smaller molecules. 2. Proteins moving from cytosol into ER, mito, peroxisomes, are transported across the membrane by protein translocators located in the membrane. Transported protein molecule musth usually unfold in order to snake through membrane 3. Proteins moving from the ER onward and from one compartment of the endomembrane system to another are transported/ferried by transport vesicles which become loaded with cargo of proteins from interior (lumen) of one compartment as they pinch off from its membrane. Discharge by fusing with target compartment membrane
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Sorting signal on proteins is continuous stretch of amino acid sequence 15-60 long. This is usually removed from finished protein once sorting has been executed. nuclear envelope encloses nuclear DNA and defines cuclear compartment. Formed from two concentric membranes, inner membrane contains proteins that act as binding sites for chromosomes and nuclear lamina (provides structural support) Composition of outer nuclear membrane is continuous with ER membrane nuclear pores form gates through which all molecules enter or leave nucleus. very large elaborate structure composed ~ 100 proteins.
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This note was uploaded on 03/24/2009 for the course BIOL 201 taught by Professor Mitchell during the Fall '07 term at UNC.

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Biol Exam II - Biol Exam II Readings Sept 11th Protein...

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