BIO 353 - Chen Exam 2 Study Guide with Complete Solutions

BIO 353 - Chen Exam 2 Study Guide with Complete Solutions endomembrane system - Ans:-A network of membranes inside and around a eukaryotic cell, related either through direct physical contact or by the transfer of membranous vesicles. Nuclear envelope, ER, GA, Lysosome, Vesicles, Endosomes, PM (plasma membrane) Two types of Protein Synthesis - Ans:-From free polyribosomes in cytosol From membrane-bound polyribosomes Polyribosome - Ans:-a mRNA that has multiple ribosomes on it progressing from 5' to 3' end Synthesis from free polyribosomes - Ans:--Makes proteins floating freely in cytosol -Does NOT make transmembrane proteins nor proteins destined for exocytosis Synthesis from membrane-bound polyribosomes - Ans:--Makes membrane associated proteins & proteins in endomembrane vesicles ©GRACEAMELIA 2024/2025 ACADEMIC YEAR. ALL RIGHTS RESERVED FIRST PUBLISH OCTOBER 2024 Page 2/26 -Present only in Eukaryotic cells Universal retention sequence for Er - Ans:--Lys-Asp-Glu -Leu-COO- KDEL How are proteins directed to target organelles? - Ans:-Sorting signals Where do proteins with no sorting signal go? - Ans:-Stay in cytosol Proteins needed in nucleus - Ans:--soluble proteins that associate with DNA How does nuclear envelope get lipids and membrane proteins? - Ans:-ER membrane is contiguous w/ nuclear envelope, so lipids and membrane proteins synthesized in ER can be transported via backfilling (aka lateral movement_ along lipid layers Nuclear Pore - Ans:-Large structures on nuclear envelope -Inner meshwork made short repeated sequences called FGs of pore proteins which prevent the passage of large molecules (lets in small hydrophilic ones) -Protein fibrils protrude on both sides (cytosolic & nuclear). Form tentacles on cytosol and a basket on nucleus ©GRACEAMELIA 2024/2025 ACADEMIC YEAR. ALL RIGHTS RESERVED FIRST PUBLISH OCTOBER 2024 Page 3/26 How does nucleus get soluble proteins for DNA? - Ans:-Proteins are transported post-translationally from cytosol (meaning in full functional form) through nuclear pores What do proteins destined for nucleus have? And what are the two functions of this thing? - Ans:-A sorting signal called a nuclear localization signal (NLS) which serves as both a mailing address to the nucleus and a ticket in What are NLSs recognized by? - Ans:-Nuclear import receptors (NIRs) aka IMPORTIN Importin - Ans:-Nuclear import receptor (NIR) How is protein import into nucleus accomplished? - Ans:--NLS on cargo protein recognized by NIR which attach to cause conformational change in complex which results in high affinity to nuclear pore tentacles in cytosol which pulls complex into the pore -NIR grabs onto FG repeats and bounce from FG to FG, plowing way into nucleus -Attract to basket to enter nucleus, NIR and cargo protein dissociate and cargo protein is delivered Ran - Ans:-GTPase (has GTP on it) that can cause conformational changes essential for translocation of protein through the NPC Ran-GAP - Ans:-Ran-GAP (GTPase Activating Protein) helps convert Ran GTP to Ran GDP via hydrolysis ©GRACEAMELIA 2024/2025 ACADEMIC YEAR. ALL RIGHTS RESERVED FIRST PUBLISH OCTOBER 2024 Page 4/26 What is on protein needing to leave the nucleus - Ans:-Nuclear export signal (NES) What attaches to NES? - Ans:-Nuclear export receptor (NER) aka exportin Exportin - Ans:-nuclear export receptor How does NIR detach from cargo protein once inside the nucleus? - Ans:-Ran attaches, cargo protein yeets off NIR-Ran complex is transferred back to cytosol How does protein export from nucleus work in regard to Ran? - Ans:-Ran needs to complex to protein and NES before it can move out. Once it moves out, Ran is yeeted off to deliver the protein How are Ran and importin/exportin recycled once in the cytosol? - Ans:-Ran GAP hydrolyzes to make GTP into GDP, separating everything to be reused How is Ran GTP replenished on nuclear side if both import and export of cargo proteins end up with Ran GDP on cytosolic side? - Ans:-Has a specialized import receptor to g