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Post Translational Modifications quiz

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  • What are post-translational modifications?
    They are changes made to proteins after they are synthesized, altering their structure or function to regulate gene expression.
  • How do chaperone proteins contribute to post-translational regulation?
    Chaperone proteins help fold polypeptide chains correctly, ensuring proteins achieve the proper structure for their function.
  • What is phosphorylation in the context of post-translational modification?
    Phosphorylation is the addition of phosphate groups to proteins, usually activating or deactivating them.
  • Which enzymes add and remove phosphate groups during phosphorylation?
    Kinases add phosphate groups, while phosphatases remove them.
  • How does phosphorylation typically affect protein activity?
    It usually activates proteins, but in some cases, it can inactivate them.
  • What is ubiquitination and what is its main effect on proteins?
    Ubiquitination is the addition of ubiquitin proteins to a target protein, marking it for degradation.
  • How does ubiquitination impact gene expression?
    By marking proteins for degradation, it removes proteins that are no longer needed, thus affecting gene regulation.
  • What are signal sequences and what is their role?
    Signal sequences are short peptide sequences that direct proteins to specific cellular locations, such as the nucleus.
  • What happens to a protein's signal sequence once it reaches its destination?
    The signal sequence is typically removed, allowing the protein to function in its new location.
  • What is the nuclear localization signal?
    It is a specific amino acid sequence that directs a protein to the nucleus.
  • How can cleavage modify a protein's function?
    Cleavage cuts sections off a protein, which can change its function or initiate a cascade of cellular events.
  • Why is protein folding important for gene expression?
    Proper folding ensures proteins are functional; misfolded proteins are destroyed and cannot contribute to gene expression.
  • Can a protein be phosphorylated more than once?
    Yes, a protein can be phosphorylated at multiple sites, sometimes hundreds or thousands of times.
  • What happens to gene expression if a protein is degraded after ubiquitination?
    Gene expression is affected because the degraded protein can no longer perform its function.
  • How do post-translational modifications regulate gene expression after translation?
    They alter protein activity, location, or stability, thereby influencing whether and how a gene's product functions in the cell.