Protein Trafficking in the Endomembrane System
30 Questions
1 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary function of the Golgi apparatus in protein trafficking?

  • Lipid biosynthesis and carbohydrate metabolism
  • Protein biosynthesis and glycosylation
  • Cargo sorting and degradation
  • Protein processing, packaging, and sorting (correct)

    • What is the name of the enclosed space within the Endoplasmic Reticulum?

  • Lumen (correct)
  • Vesicles
  • Golgi apparatus
  • Cisternae

    • Which type of Endoplasmic Reticulum is involved in lipid biosynthesis?

  • Rough and Smooth ER
  • Smooth ER (correct)
  • ER Lumen
  • Rough ER

    • What is the primary function of the Endosome in protein trafficking?

    <p>Cargo sorting</p> Signup and view all the answers

    What is the approximate percentage of total cell membrane that can be made up of Endoplasmic Reticulum?

    <p>50%</p> Signup and view all the answers

    What is the role of resident ER biosynthetic enzymes in lipid biosynthesis?

    <p>To manufacture membrane lipids from glycerol and fatty acid precursors</p> Signup and view all the answers

    What is the primary function of Scrambolase in the lipid bilayer?

    <p>To scramble lipids and spread out the lipid bilayer</p> Signup and view all the answers

    What is the primary function of Cytochrome P-450 in the smooth ER of the liver?

    <p>To hydroxylate substrates</p> Signup and view all the answers

    What is the primary function of the rough ER?

    <p>To translate mRNAs into secretory proteins</p> Signup and view all the answers

    What is the fate of non-endomembrane proteins during protein synthesis?

    <p>They stay in the cytosol</p> Signup and view all the answers

    What is the primary function of Glucose-6-phosphatase in the smooth ER?

    <p>To break down stored glycogen into glucose</p> Signup and view all the answers

    What is the primary function of membrane transporters in the context of calcium ions?

    <p>To pump calcium ions into the ER lumen for storage</p> Signup and view all the answers

    What direction do kinesin motor proteins move vesicles?

    <p>Towards the cell periphery</p> Signup and view all the answers

    What is the primary function of the Golgi apparatus in protein trafficking?

    <p>Modifying and sorting proteins</p> Signup and view all the answers

    Which enzyme is predominantly localized to the medial cisternae of the Golgi apparatus?

    <p>Glucosamine transferase I</p> Signup and view all the answers

    What is the role of the Trans Golgi Network in protein trafficking?

    <p>Sorting vesicles and secretory protein cargo</p> Signup and view all the answers

    What is the result of differential glycosylation patterns in secretory proteins?

    <p>Structure and function diversity</p> Signup and view all the answers

    In which direction do dynein motor proteins move vesicles?

    <p>Towards the cell interior</p> Signup and view all the answers

    What is the primary function of the ER signal sequence?

    <p>To recognize and transport nascent secretory proteins into the ER</p> Signup and view all the answers

    What is the role of the Signal Recognition Particle (SRP) in protein synthesis?

    <p>To recognize and transport the signal sequence to the ER</p> Signup and view all the answers

    What is the main function of chaperones in the ER?

    <p>To assist with protein folding</p> Signup and view all the answers

    What is the primary site of protein glycosylation initiation?

    <p>The ER</p> Signup and view all the answers

    What is the primary difference between N-linked and O-linked glycosylation?

    <p>The type of amino acid involved</p> Signup and view all the answers

    What is the function of the 'stop transfer' anchor signal in newly translated membrane-associated proteins?

    <p>To help them stay embedded within the ER membrane</p> Signup and view all the answers

    Where does O-linked glycosylation occur?

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

    What is the role of calnexin in glycosylation?

    <p>Capturing and promoting proper folding of proteins</p> Signup and view all the answers

    What is the function of UDP-glucose:glycoprotein glucosyltransferase (UGGT) enzymes?

    <p>Sensing proper folding of proteins</p> Signup and view all the answers

    What happens to misfolded proteins in the ER?

    <p>They are degraded via ERAD</p> Signup and view all the answers

    What is the role of COPII vesicles in the secretory pathway?

    <p>Packaging proteins into vesicles and sending them to the Golgi</p> Signup and view all the answers

    What is the final step of the secretory pathway?

    <p>Exocytosis at the plasma membrane</p> Signup and view all the answers

    Study Notes

    Endomembrane System and Protein Trafficking

    • Multiple organelles are involved in moving macromolecules (proteins) in and out of the cell.
    • The rough Endoplasmic Reticulum (rER) is responsible for membrane/secretory protein biosynthesis, glycosylation, and folding.
    • The Golgi apparatus is involved in protein processing, packaging, and sorting.
    • Plasma membrane endomembrane vesicles are part of the trafficking system.
    • Endosomes are responsible for cargo sorting, and lysosomes are responsible for degradation.

    Endoplasmic Reticulum (ER)

    • ER is a continuous network of flattened sacs or cisternae.
    • The ER can make up around 50% of the total cell membrane.
    • Rough ER has ribosomes attached to its membrane and is involved in synthesizing membrane/secretory proteins.
    • Smooth ER lacks ribosomes and is involved in lipid biosynthesis, Ca++ storage, and drug detoxification.
    • The ER lumen is the site of initial protein glycosylation and folding.
    • Rough and smooth ER membranes are contiguous with each other and the nuclear envelope.

    Rough ER

    • Rough ER is studded with ribosomes that synthesize secretory and endomembrane system resident proteins.
    • All mRNAs initially associate with cytosolic ribosomes, but secretory proteins are immediately trafficked to the ER for translation.

    Smooth ER

    • Smooth ER synthesizes membrane lipids, such as phospholipids, from glycerol, fatty acid precursors, and various polar head groups.
    • Scramblase scrambles lipids to spread out the lipid bilayer.
    • Smooth ER also stores/sequesters Ca++ and contains enzymes that metabolize foreign chemicals, such as cytochrome P-450.
    • Smooth ER aids in glycogen metabolism, breaking down stored glycogen into glucose.

    Protein Trafficking

    • Secretory proteins "traffic" from the ER to the Golgi and then out towards the plasma membrane via vesicles.
    • Vesicle transport occurs along microtubule "train tracks" using ATP-dependent motor proteins, such as kinesin and dynein.
    • The Golgi apparatus is a processing/sorting station for endomembrane and secretory proteins, modifying and directing cargo through post-translational modifications and packaging.

    Golgi Apparatus

    • The Golgi apparatus consists of an ordered series of compartments, including cis, medial, and trans cisternae.
    • Each Golgi compartment is biochemically distinct and contains specific resident enzymes.
    • The Golgi apparatus is responsible for post-translational modifications, such as differential glycosylation, phosphorylation, and sulfation.
    • The Golgi apparatus also plays a role in trafficking lipids.

    Post-Translational Modifications

    • The Golgi apparatus terminally N-glycosylates secretory proteins, allowing for structure and function diversity.
    • Trans Golgi network sorts vesicles/secretory protein cargo based on "signals/motifs" built into the cargo.
    • ER signal sequence is required for cotranslational import of nascent secretory proteins into the ER.
    • Signal recognition particle (SRP) recognizes the signal sequence and transports the translating ribosome to the ER.

    Protein Glycosylation

    • Protein glycosylation (polysaccharide) initiates in the ER and finishes in the Golgi.
    • Chaperones assist with protein folding, and carbohydrate transferase enzymes add "core" sugar moieties onto the growing polypeptide chain.
    • "N-linked" glycosylation occurs on asparagine residues, while "O-linked" glycosylation occurs on serine or threonine residues.
    • Core glycosylation promotes proper protein folding in the ER via calnexin.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Description

    Learn about the process of protein trafficking in the endomembrane system, including the roles of different organelles such as the rER, Golgi, plasma membrane, endosomes, and lysosomes. Understand how proteins are synthesized, processed, and transported in and out of the cell.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser