BIOL 3510 1st Edition Lecture 16 Outline of Last Lecture I Parts of the Chloroplast II Photosystems III Charge Separation IV Noncyclic Photophosphorylation V Carbon Fixation in the Stroma VI Uses of Glyceraldehyde 3 phophate Outline of Current Lecture I Organelles II Mechanisms of Protein Transport into Organelles III Peroxisomes Current Lecture Cells contain many membrane enclosed organelles Organelles perform diverse functions Cytosol metabolic pathways protein synthesis Nucleus contains nuclear genome DNA and RNA synthesis Mitochondria ATP synthesis by oxidative phosphorylation Chloroplasts ATP synthesis and carbon fixation by photosynthesis Endoplasmic reticulum ER membrane synthesis protein distribution o Rough ER ribosomes attached o Smooth ER Ca 2 sequestration etc Golgi apparatus proteins and lipid modification and sorting Lysosomes intracellular degradation Endosomes sorting of endocytosed material Peroxisomes oxidation of toxic molecules Three Mechanisms of Protein Transport into Organelles 1 Transport through nuclear pore folded proteins enter through nuclear pores 2 Transport across membrane unfolded proteins enter organells via protein translocators 3 Transport by vesicles folded proteins move via transport vesicles that fuse with destination membranes 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 Folded proteins with nuclear localization signals NLS are bound by import receptors Nuclear import receptors and cargo cross the nuclear envelope via the nuclear pore Ran GTP binds to the nuclear import receptor in the nucleus and returns it to the cytoplasm Ran GAP GTPase activating protein and RAN GEF guanine exchange factor mediate the activity of Ran Unfolded proteins enter mitochondria and chloroplasts via protein translocators Chaparones that bind unfolded proteins and hydrolyze ATP drive import into the mitochondria Peroxisomes Contain oxidative enzymes Use O2 and H2O2 to remove protons Break down fatty acids Involved in the formation of plasmalogen a phopholipid needed for neuron function Import proteins via the action of peroxins that use ATP as n energy source exact mechanism is unclear Rough ER contains bound ribosomes When translating proteins with ER signal sequences ribosomes are targeted to the ER ER protein targeting depends on the interaction between the signal recognition particle SRP and the SRP receptor ER proteins are threaded through a protein translocator After signal sequence cleavage soluble proteins are released into the ER lumen The arrangement of ER membrane proteins is determined by hydrophobic start transfer and stop transfer sequences The location of positively charged amino acids determines the orientation of protein insertion Before the start transfer N terminus is cytosolic After the start transfer N terminus is luminal
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