Golgi Apparatus: Discovery and Structure
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Questions and Answers

Who discovered the Golgi apparatus?

  • Camillo Golgi (correct)
  • Louis Pasteur
  • Robert Hooke
  • Rudolf Virchow

    • What characteristic defines the two sides of the Golgi apparatus?

  • Both sides are similar in structure.
  • CIS side is convex, TRANS side is concave. (correct)
  • CIS side is concave, TRANS side is convex.
  • Both sides are flat and unremarkable.

    • What method did Golgi use to stain the Golgi apparatus for observation?

  • Electron microscopy
  • Fluorescence microscopy
  • Silver impregnation technique (correct)
  • Dye infusion method

    • What is the primary function of the Golgi apparatus?

    <p>Protein glycosylation and sorting</p> Signup and view all the answers

    What happens to vesicles when they fuse with the CIS side of the Golgi apparatus?

    <p>They are delivered into the GA for processing.</p> Signup and view all the answers

    How does the Golgi apparatus contribute to lipid biosynthesis?

    <p>It modifies and assembles lipids into vesicles.</p> Signup and view all the answers

    What distinguishes the sugar pattern of products exiting from the TRANS side of the Golgi apparatus?

    <p>It defines their final destination.</p> Signup and view all the answers

    What directional communication exists between the ER and Golgi apparatus?

    <p>Bidirectional communication.</p> Signup and view all the answers

    What is the primary function of receptors located in the trans-golgi network?

    <p>Sorting and targeting proteins to their final destinations</p> Signup and view all the answers

    What best describes constitutive secretion?

    <p>It occurs continuously without the need for external signals</p> Signup and view all the answers

    In regulated secretion, vesicles remain in the cytoplasm until which event occurs?

    <p>The vesicles receive a signal, such as an increase in intracellular calcium levels</p> Signup and view all the answers

    What is the main role of the Golgi apparatus in the production of carbohydrates?

    <p>Modifying and adding sugar residues to glycoproteins and glycolipids</p> Signup and view all the answers

    Which of the following structures is primarily associated with the Golgi apparatus?

    <p>Stacks of flattened membrane sacs</p> Signup and view all the answers

    What characterizes regulated secretion in secretory vesicles?

    <p>Vesicles are stored in the cytoplasm and released upon receiving a signal.</p> Signup and view all the answers

    Which of the following describes the function of lysosomes?

    <p>They carry out digestion using hydrolytic enzymes.</p> Signup and view all the answers

    What occurs during retrograde transport in cells?

    <p>Proteins are moved back to the cis Golgi network and ER.</p> Signup and view all the answers

    Which of the following best describes the cisternal maturation model of the Golgi apparatus?

    <p>New membranes continuously alter the composition of each cisternae over time.</p> Signup and view all the answers

    What are secretory vesicles responsible for?

    <p>Exocytosis of proteins and neurotransmitters.</p> Signup and view all the answers

    What is the primary role of retrograde transport vesicles?

    <p>To return proteins to the ER that have completed their function.</p> Signup and view all the answers

    What type of enzymes are primarily found in lysosomes?

    <p>Hydrolytic enzymes.</p> Signup and view all the answers

    Which statement is true regarding the transport of proteins through the Golgi apparatus?

    <p>Vesicle transport can occur in both anterograde and retrograde directions.</p> Signup and view all the answers

    What is the main function of glycosylation that occurs in the Golgi Apparatus (GA)?

    <p>To modify glycosylation of proteins.</p> Signup and view all the answers

    Which type of glycosylation involves the addition of sugars to asparagine residues?

    <p>N-glycosylation</p> Signup and view all the answers

    What is the outcome when mannose residues added during glycosylation are phosphorylated?

    <p>They serve as a tagging mechanism for lysosomal targeting.</p> Signup and view all the answers

    How do complex glycosylations differ from mannose glycosylations?

    <p>Complex glycosylations can add a variety of sugars while mannose glycosylations only add mannose.</p> Signup and view all the answers

    Which amino acids are primarily involved in O-glycosylations?

    <p>Serine and threonine</p> Signup and view all the answers

    What is the primary endpoint of proteins modified by complex glycosylation?

    <p>They typically follow the secretion pathway.</p> Signup and view all the answers

    What essential components does the Golgi Apparatus synthesize by adding sugars?

    <p>Glycosaminoglycans and proteoglycans</p> Signup and view all the answers

    What happens to the oligosaccharide that enters the CGN of the Golgi Apparatus?

    <p>Only the central part is retained after modification.</p> Signup and view all the answers

    What is the primary characteristic of the Golgi apparatus that confirms its polarized nature?

    <p>It has two distinct sides: CIS and TRANS.</p> Signup and view all the answers

    Which two modifications can occur to ceramide in the Golgi apparatus?

    <p>Addition of sugars and phosphocholine.</p> Signup and view all the answers

    What does the cisternal maturation model describe in the Golgi apparatus?

    <p>The constant fusion of new membranes from the ER and maturation of cisternae.</p> Signup and view all the answers

    How do vesicles exiting the Golgi apparatus reach their targets?

    <p>Through secretory pathways that vary by destination.</p> Signup and view all the answers

    Which process is responsible for adding sugars to proteins in the Golgi apparatus?

    <p>Glycosylation.</p> Signup and view all the answers

    What is the role of receptors in the Golgi apparatus regarding glycosylated proteins?

    <p>To recognize specific glycosylation patterns.</p> Signup and view all the answers

    Which mechanism describes the movement of proteins through the Golgi apparatus?

    <p>Vesicle transport model.</p> Signup and view all the answers

    What is one potential destination for vesicles exiting the Golgi apparatus?

    <p>Secretory vesicles.</p> Signup and view all the answers

    Study Notes

    Golgi Apparatus Discovery

    • Camillo Golgi discovered the Golgi apparatus in 1898 using a silver impregnation technique
    • This technique involved precipitating silver metals in areas rich in Golgi apparatus, staining them
    • The discovery was initially observed in spinal ganglion neurons

    Golgi Apparatus Structure

    • The Golgi apparatus is composed of a stack of flattened, membrane-bound sacs called cisternae
    • These cisternae are close together but not connected
    • It's a polarized organelle with two distinct sides:
      • The cis side receives vesicles from the endoplasmic reticulum (ER)
      • The trans side releases vesicles containing sorted contents
    • The cis side is convex, while the trans side is concave
    • Vesicles leaving the trans side are sorted based on their sugar patterns, allowing for cell-specific recognition

    Golgi Apparatus Functions

    • The Golgi apparatus is the "director" of vesicle trafficking
    • It modifies and sorts proteins received from the ER
    • It packages and labels proteins for their final destinations:
      • Secretory vesicles:
        • Constitutive secretion: continuous release of proteins without specific signals
        • Regulated secretion: vesicles are stored in the cytoplasm and released only when triggered by a specific signal
      • Lysosomes: membrane-bound vesicles containing hydrolytic enzymes, tagged with mannose-6-phosphate
      • Retrograde transport vesicles: transport proteins back to the ER or cis Golgi to maintain ER function
    • Different cisternae contain specific enzymes, enabling sequential enzymatic reactions during protein modification
    • Proteins leaving the trans Golgi network (TGN) are already sorted according to their destination

    Movement of Contents Across the Golgi Apparatus

    • Two mechanisms coexist:
      • Cisternal Maturation Model:
        • The Golgi constantly receives new membranes from the ER, which fuse with the cis side
        • This pushes older cisternae towards the trans side, causing them to mature
        • As cisternae mature, their enzyme content changes, requiring enzymes to be retro-transported to maintain their positions
      • Vesicle Transport Model:
        • Vesicles bud off from the edges of the Golgi, moving contents back and forth (anterograde and retrograde)

    Protein Glycosylation In The Golgi Apparatus

    • The Golgi apparatus modifies and adds sugar residues to proteins already glycosylated in the ER
    • Proteins entering the cis Golgi network (CGN) have the same oligosaccharide (14 residues) attached to asparagine amino acids
    • This oligosaccharide is further modified in the Golgi, ultimately leaving only 5 residues
    • Glycosylation occurs through two patterns:
      • Complex glycosylation: various sugars are added to the central oligosaccharide, marking proteins for the secretory pathway (membrane and secretion proteins)
      • Mannose glycosylation: only mannose monomers are added, and phosphorylation of these residues tags proteins for delivery to lysosomes
      • N-glycosylation: sugars are added to the nitrogen atom of asparagine amino acids, started in the ER but finalized in the Golgi
      • O-glycosylation: sugars are added to the oxygen atom of serine and threonine amino acids, unique to the Golgi apparatus

    GAG and PG Synthesis In The Golgi Apparatus

    • The Golgi synthesizes important components of the extracellular matrix (ECM) through glycosylation
    • This process involves adding specific sugars to lipids, such as ceramide
    • Two main modifications of ceramide occur in the Golgi:
      • Adding sugars to create glycolipids
      • Adding phosphocholine to create sphingomyelin, a major lipid in cell membranes

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    Description

    Explore the fascinating discovery of the Golgi apparatus by Camillo Golgi in 1898 and its unique structure made up of cisternae. This quiz covers its function in vesicle trafficking and its role in modifying and sorting proteins within the cell.

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