🌟 Fun Fact: Proteins in our cells don’t last forever! Just like we recycle plastic and paper, our cells recycle proteins. 🔄

• Proteins made by translation don’t hang around for long.
• Why? Several reasons!
  • 🔁 Changing Needs: Cells change activities. For instance, when a cell moves from one phase of its life cycle to the next, it might not need a certain protein anymore.
    • 🌍 Real-World Example: Just like outgrowing childhood toys when you become a teenager, cells outgrow certain proteins as they move through stages.
  • 🧪 Chemical Damage: Some proteins are sensitive and can be altered by free radicals or other reactive chemicals. Once changed, they can't do their jobs.
    • 🌍 Real-World Example: Imagine if coffee spilled on your laptop. It won't work properly, right? Similarly, when proteins get "damaged," they can't function.
  • 🌡️ Misfolding: Sometimes proteins can get twisted, misshaped, or denatured.
    • 🌍 Real-World Example: Like when you accidentally shrink your favorite sweater in the wash - it doesn’t fit or function as it used to!

• When proteins can't do their jobs or are not needed, proteasomes break them down.
  • 🔍 Appearance: Check out the proteasome structure in your textbook!
• Ubiquitin Tagging: If a protein is destined for recycling, it gets a 'tag' with small proteins called ubiquitin.
  • 🌍 Real-World Example: Think of ubiquitin as the recycling symbol ♻️, indicating the protein is ready for the recycling bin!
• Proteasome Process
  • Entry: The ubiquitinated proteins get recognized by the proteasome’s regulatory subunits.
  • Unfolding: The proteins are unfolded and sent into the proteasome’s central chamber. This action needs energy from ATP.
  • Digestion: Inside the proteasome, multiple proteases break the proteins into shorter amino acid chains.
  • Exit & Recycling: These short chains leave the proteasome and are further digested in the cytoplasm. This process gives amino acids which the cell can use to make new proteins.
    • 🌍 Real-World Example: This is like breaking down an old wooden chair to reuse the wood to build a new table.