Golgi Apparatus Flashcards

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1
Q

How do proteins/lipids enter the Golgi network?

A

Packaged into vesicles coated with protein COPII which merge to form a vesicular tubular cluster, which then travels along the microtubules to merge with the cis-Golgi network

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2
Q

How do membrane proteins ensure that they reach the membrane?

A

Have specific exit signals which can be di-acidic (2Glu, 2Asp) or di-hydrophobic (2*Met)

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3
Q

How are resident ER proteins retrieved?

A
  • Via ER retrieval motif KDEL

- Receptors bind to this and form COPI coat to retrieve proteins

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4
Q

What is the structure of the Golgi apparatus?

A
  • Made from lipid sacks called cisternae

- Proteins/lipids join as the cis-face and leave at the trans-face

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5
Q

What does the N-linked glycosylation of a protein depend on?

A

Composition of the protein, its destination, how fast it’s going and what enzymes are present -> determines protein fate

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6
Q

How does N-linked glycolisation occur?

A

Via the addition and removal of sugars via glycosiletransferases and glycosidases

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7
Q

What is O-linked glycolisation and when is it used?

A
  • Linked to serine/threonine molecules
  • Addition of one sugar at a time and only a few oligosaccharides
  • Common in many cytoplasmic/nuclear proteins and transcription factors
  • Present in eukaryotes, bacteria and archea
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8
Q

Describe the process of sphingomyelin and glycolipid synthesis

A

Ceramide (sphingosine+fatty acid) can have added a phosphorylcholine group to form sphingomyelin or sugar residues to form glycolipids

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9
Q

Name 5 other Golgi-mediated modifications

A
  • Sulfation of tyrosine residues
  • Phosphorylation
  • Proteolytic processing
  • Palmitoylation
  • Oligomerisation
    (Happen at different places in the Golgi apparatus)
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10
Q

What is the difference between the vesicular transport model and the cisternal maturation model?

A

vesicular transport - molecules all move in small vesicles, however energetically unfeasible and some proteins are too big
cisternal maturation - Entire stack moves forward, only Golgi enzymes are transported back by vesicles

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11
Q

How does the trans-Golgi network ensure that proteins are delivered to the correct location?

A
  • Protein markers attached

- One of the most common being mannose-6-phosphate which signals for lysosome

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12
Q

How is mannose-6-phosphate produced?

A

Phosphorylation by UDP addition and loss of N-acetylglucosamine

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13
Q

What is the difference between constituive and regulated secretory pathways?

A

Constituive is unregulated

Regulated is controlled by various proteins and molecules such as neurotransmitters and hormones

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