Cell Biology: Protein Sorting and Folding
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Questions and Answers

What is the primary function of the signal recognition particle (SRP)?

  • To initiate cotranslational translocation (correct)
  • To degrade malfunctioning proteins
  • To modify proteins after translation
  • To transport proteins solely to lysosomes
  • Which post-translational modification is primarily associated with the regulation of protein activity?

  • Ubiquitination
  • Acetylation
  • Phosphorylation (correct)
  • Hydroxylation
  • Which post-translational modification is specifically important for collagen synthesis?

  • Phosphorylation
  • Hydroxylation (correct)
  • Ubiquitination
  • Acetylation
  • What is the main role of ubiquitination in post-translational modifications?

    <p>To facilitate protein degradation</p> Signup and view all the answers

    Cotranslational translocation refers to which process?

    <p>Synthesis and movement of proteins to the endoplasmic reticulum during translation</p> Signup and view all the answers

    Which modification is primarily involved in gene regulation?

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

    What is the primary enzyme responsible for introducing ubiquitin to target proteins?

    <p>Ubiquitin ligases</p> Signup and view all the answers

    Which of the following modifications requires the addition of a phosphate group?

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

    What is the primary role of post-translational modifications in proteins?

    <p>They enhance the functional diversity of proteins.</p> Signup and view all the answers

    Which of the following accurately describes protein sorting?

    <p>It directs proteins to their specific cellular destinations.</p> Signup and view all the answers

    What is the function of signal peptides in protein targeting?

    <p>They target proteins to specific organelles.</p> Signup and view all the answers

    Which organelle requires a mitochondrial presequence for protein import?

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

    In the context of protein targeting, what role do chaperones play?

    <p>They assist in folding proteins and transporting them.</p> Signup and view all the answers

    What is one result of improper protein sorting or modifications?

    <p>Cellular dysfunction and disease.</p> Signup and view all the answers

    Why is protein targeting important for cellular functions?

    <p>It allows proteins to reach their functional sites in the cell.</p> Signup and view all the answers

    Which protein modification type is most directly involved in increasing protein diversity?

    <p>Covalent modifications after synthesis.</p> Signup and view all the answers

    Study Notes

    Protein Sorting

    • Protein sorting, or protein targeting, refers to the process of directing proteins to their specific locations within a cell.
    • Signal peptides are specific amino acid sequences that act as address labels, guiding proteins to their correct destinations.
    • Proteins with a mitochondrial presequence are transported to mitochondria.
    • Proteins with a peroxisomal targeting signal are transported to peroxisomes.
    • Cotranslational translocation is a process where proteins are synthesized and transported to the endoplasmic reticulum (ER) simultaneously. It involves the signal recognition particle (SRP).

    Protein Folding

    • Proteins fold into complex three-dimensional structures that determine their function.
    • Incorrect folding can lead to protein misfolding, a common cause of various diseases.

    Post-Translational Modifications

    • Post-translational modifications are covalent modifications that occur after a protein has been synthesized.
    • These modifications enhance the functional diversity of proteins and can influence protein sorting.
    • Phosphorylation is the addition of a phosphate group to a protein, often regulated by kinases. This modification is involved in regulating protein activity.
    • Hydroxylation is the addition of a hydroxyl group (-OH) to a protein. This modification is crucial in the synthesis of collagen.
    • Ubiquitination involves the attachment of ubiquitin, a small protein, to a target protein. This process typically leads to protein degradation.
    • Acetylation is the addition of an acetyl group (-CO-CH3) to a protein. This modification plays a role in gene regulation.

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    Description

    This quiz explores the crucial concepts of protein sorting, folding, and post-translational modifications. Learn how proteins are directed to specific cellular locations and the significance of their three-dimensional structures. Test your knowledge on signal peptides, cotranslational translocation, and the implications of protein misfolding.

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