Cell and Molecular Biology: Endoplasmic Reticulum Functions
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Questions and Answers

What is the main function of the endoplasmic reticulum (ER) in an animal cell?

  • Energy production and storage
  • DNA replication and repair
  • Protein modification and quality control (correct)
  • Lipid degradation and recycling

    • Which structure within the ER plays a key role in transferring preformed precursor oligosaccharides to proteins?

  • Calreticulin
  • Membrane-bound oligosaccharide transferase (correct)
  • Chaperon proteins
  • Calnexin

    • What is the role of N-glycosylation in the ER related to protein folding?

  • Promoting protein degradation
  • Regulating lipid biosynthesis
  • Initiating protein synthesis
  • Preventing folding intermediates from aggregating (correct)

    • Which proteins in the ER bind to oligosaccharides on folding intermediates to help with correct protein folding?

    <p>Calnexin and calreticulin</p> Signup and view all the answers

    What distinguishes folding intermediates from mis-folded proteins in the ER during protein processing?

    <p>N-glycans acting as timers</p> Signup and view all the answers

    Which process in the ER involves the covalent addition of oligosaccharides to proteins?

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

    What is the significance of trimming a mannose on the core Nglycan of a protein?

    <p>Marks the protein for degradation</p> Signup and view all the answers

    Why do proteins that fold and exit the ER faster than mannose trimming occur avoid degradation?

    <p>They are recognized by chaperones for proper folding</p> Signup and view all the answers

    What role do Glucosyltransferases play in the ER quality control process?

    <p>Add glucose to oligosaccharides that have lost their final glucose but not properly folded</p> Signup and view all the answers

    What is the main function of calnexin and calreticulin in recognizing N-linked glycans?

    <p>Recognize N-linked glycans with a single terminal glucose</p> Signup and view all the answers

    How does the unfolded protein response (UPR) get triggered in the ER?

    <p>Activation of ER membrane proteins by misfolded proteins</p> Signup and view all the answers

    What is the role of PERK in the unfolded protein response (UPR)?

    <p>Phosphorylating and inhibiting translation initiation factor to reduce new protein production</p> Signup and view all the answers

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