Protein Modification in the ER
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Questions and Answers

What triggers the synthesis of chaperones and other quality control proteins?

  • Accumulation of unfolded proteins in the ER (correct)
  • Reduced demand for protein folding
  • Increase in protein synthesis rate
  • Depletion of cholesterol in the ER membrane

    • What is the primary function of the Golgi apparatus in the secretory pathway?

  • Protein synthesis
  • Protein degradation
  • Vesicle formation
  • Protein modification and sorting (correct)

    • What determines the size of the ER?

  • Demand for protein folding (correct)
  • ER membrane fluidity
  • Availability of chaperones
  • Rate of protein synthesis

    • Which of the following is NOT a function of the secretory pathway?

    <p>Protein synthesis</p> Signup and view all the answers

    What is the primary function of the cis and trans regions of the Golgi apparatus?

    <p>Protein modification and sorting</p> Signup and view all the answers

    What is the primary function of chaperone proteins in the ER?

    <p>To ensure proper protein folding and prevent misfolding</p> Signup and view all the answers

    Which of the following is NOT a consequence of accumulation of misfolded proteins in the ER?

    <p>Stimulation of vesicle transport to the plasma membrane</p> Signup and view all the answers

    What is the primary function of glycosylation in the ER?

    <p>To protect proteins from degradation and guide them to the proper organelle</p> Signup and view all the answers

    Where do proteins undergo glycosylation in the secretory pathway?

    <p>In the ER lumen</p> Signup and view all the answers

    What is the purpose of the unfolded protein response (UPR) in the ER?

    <p>To degrade misfolded proteins and maintain ER homeostasis</p> Signup and view all the answers

    What is the primary route that proteins follow to reach the Golgi apparatus, endosomes, lysosomes, and the cell surface?

    <p>First entering the ER from the cytosol</p> Signup and view all the answers

    What happens to water-soluble proteins when they enter the ER?

    <p>They cross the ER membrane completely and are released into the lumen</p> Signup and view all the answers

    What is the function of the ER in protein trafficking?

    <p>To modify and package proteins into vesicles</p> Signup and view all the answers

    What is the fate of transmembrane proteins in the ER?

    <p>They only partially cross the ER and become embedded in the membrane</p> Signup and view all the answers

    What is the common feature of all proteins synthesized by ribosomes in the nucleus?

    <p>They are all synthesized by a common pool of ribosomes</p> Signup and view all the answers

    What is the role of the signal sequence in directing proteins to the ER?

    <p>To open the translocation channel</p> Signup and view all the answers

    During protein synthesis, what happens to the signal sequence?

    <p>It is recognized by the SRP</p> Signup and view all the answers

    What is the function of the SRP?

    <p>To recognize and bind to the signal sequence</p> Signup and view all the answers

    What happens to proteins that are being synthesized and enter the ER?

    <p>They enter the lumen of the ER</p> Signup and view all the answers

    What is the role of the signal sequence in transmembrane protein arrangement?

    <p>To determine the orientation of the protein in the lipid bilayer</p> Signup and view all the answers

    What is the function of signal sequences in protein sorting?

    <p>To direct proteins to the correct compartment</p> Signup and view all the answers

    What is the mechanism by which proteins enter the nucleus?

    <p>Through nuclear pores</p> Signup and view all the answers

    What is the term for the process by which a vesicle fuses with the plasma membrane, releasing its contents to the cell's surroundings?

    <p>Exocytosis</p> Signup and view all the answers

    Which of the following is a destination for proteins that enter the endoplasmic reticulum while being synthesized?

    <p>The ER lumen</p> Signup and view all the answers

    What is the term for the process by which extracellular materials are captured by vesicles that bud inward from the plasma membrane?

    <p>Endocytosis</p> Signup and view all the answers

    In which part of the Golgi apparatus does the additional glycosylation and sorting of proteins occur?

    <p>Trans face</p> Signup and view all the answers

    What is the mechanism by which secretory proteins are released from the cell?

    <p>Exocytosis</p> Signup and view all the answers

    What is the purpose of the constitutive exocytosis pathway in eukaryotic cells?

    <p>To operate continually in all eukaryotic cells</p> Signup and view all the answers

    What is the environment of the trans-Golgi network that is essential for the formation of secretory vesicles?

    <p>Acidic pH and high calcium concentration</p> Signup and view all the answers

    What is the process by which secretory vesicles release their contents in response to a signal?

    <p>Vesicle docking and fusion</p> Signup and view all the answers

    Where do the bulk of proteins that enter peroxisomes come from?

    <p>The cytosol</p> Signup and view all the answers

    What is the import signal for proteins entering peroxisomes?

    <p>SKL (ser-lys-leu)</p> Signup and view all the answers

    What is a consequence of mutations that block peroxisomal protein import?

    <p>Zellweger syndrome</p> Signup and view all the answers

    How do proteins enter peroxisomes from the cytosol?

    <p>Via protein translocators</p> Signup and view all the answers

    What is the function of peroxisomal enzymes?

    <p>Breakdown of toxins, alcohols, and fatty acids</p> Signup and view all the answers

    Do proteins need to unfold to enter peroxisomes?

    <p>No, protein translocators allow direct import</p> Signup and view all the answers

    Which organelle is involved in protein synthesis and transport?

    <p>Endoplasmic reticulum</p> Signup and view all the answers

    What is the function of protein receptors in protein transport?

    <p>To recognize and bind specific proteins</p> Signup and view all the answers

    Which pathway is involved in the transport of proteins from the cytosol to peroxisomes?

    <p>Protein targeting pathway</p> Signup and view all the answers

    What is the fate of individuals with Zellweger syndrome?

    <p>They usually do not survive beyond 6 months</p> Signup and view all the answers

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