Protein Synthesis and Translocation in ER
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Questions and Answers

What is the function of dolichol phosphate molecule in protein glycosylation?

  • It acts as an enzyme to catalyze the addition of sugars to proteins.
  • It is involved in recognizing the signal sequence on nascent proteins.
  • It provides a hydrophobic environment for glycosylation to occur.
  • It acts as a carrier molecule to transfer sugars to proteins in the ER. (correct)

    • What happens to N-glycosylation in mutations that disrupt the protein translocation process?

  • N-glycosylation occurs normally regardless of mutations in the translocation process.
  • N-glycosylation does not occur at all in mutated proteins.
  • N-glycosylation is delayed and inefficient due to improper protein folding. (correct)
  • N-glycosylation is enhanced due to increased availability of sugar substrates.

    • Which best describes the role of Signal Recognition Particle (SRP) in protein synthesis?

  • SRP helps in folding proteins correctly within the rough ER.
  • SRP helps in the translocation of ribosomes from rough ER to smooth ER.
  • SRP binds to the signal sequence and ribosome, aiding in targeting nascent proteins to the ER membrane. (correct)
  • SRP catalyzes the cleavage of signal sequences from nascent proteins.

    • What is the primary function of Rough Endoplasmic Reticulum (RER) in protein synthesis?

    <p>Involved in co-translational translocation of secretory and membrane proteins.</p> Signup and view all the answers

    Which statement accurately describes the synthesis of integral membrane proteins?

    <p>Integral membrane proteins are co-translationally inserted into the ER membrane.</p> Signup and view all the answers

    When SRP binds to both the signal sequence on nascent protein and ribosome, what is the next step in protein synthesis?

    <p>SRP-ribosome-nascent protein complex is recruited to the RER membrane.</p> Signup and view all the answers

    What is the role of the translocon in protein synthesis?

    <p>Facilitates the movement of the nascent polypeptide from the ribosome to the ER lumen</p> Signup and view all the answers

    How do G-proteins regulate protein synthesis in the context of the text?

    <p>By binding either GTP or GDP molecules and acting as molecular switches</p> Signup and view all the answers

    What is the function of SRP in protein synthesis according to the text?

    <p>Guides ribosomes that are synthesizing membrane proteins to the ER membrane</p> Signup and view all the answers

    Which statement accurately describes G-proteins in protein synthesis?

    <p>They act as molecular switches by changing conformation based on GTP or GDP binding</p> Signup and view all the answers

    Which molecule is essential for N-glycosylation in protein synthesis?

    <p>Dolichol phosphate</p> Signup and view all the answers

    What impact would mutations affecting N-glycosylation have on protein function?

    <p>Impaired protein folding and stability</p> Signup and view all the answers

    How is the dolichol phosphate molecule involved in protein glycosylation?

    <p>It serves as the site for attachment of sugars on the cytosolic side of the membrane.</p> Signup and view all the answers

    What happens once the oligosaccharide is completely assembled in glycosylation?

    <p>It is enzymatically transferred to an asparagine residue of the nascent polypeptide.</p> Signup and view all the answers

    What is the consequence of mutations leading to total absence of N-glycosylation?

    <p>Death of embryos before implantation.</p> Signup and view all the answers

    How are mutations affecting partial disruption of the glycosylation pathway in the ER different from mutations causing total absence of N-glycosylation?

    <p>They lead to serious inherited disorders affecting various organ systems.</p> Signup and view all the answers

    In protein synthesis, what role does SRP (signal recognition particle) play?

    <p>It assists in targeting proteins to their correct cellular location.</p> Signup and view all the answers

    What happens after the dolichol-PP is flipped back across the membrane during protein glycosylation?

    <p>It is ready to begin accepting sugars again.</p> Signup and view all the answers

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