Cytology · MU Pleven

Topic 12. Membranous cell organelles. Golgi apparatus, Secretory vesicles, coated vesicles.

Explains the Golgi apparatus as a packaging organelle: its cis and trans faces, how it checks, sorts and modifies proteins from the RER, and the three destinations of its secretory vesicles. Then covers the three vesicle types (secretory, coated and transport) and the vesicular transport processes of endocytosis (phagocytosis, pinocytosis, receptor-mediated) and exocytosis, with a summary table of these processes and their examples.

Inside: 2 sections · 2 labelled pictures · 1 table · 15 flashcards · 5 min

Topic 12 of 59 in the MU Pleven syllabus for Cytology (Medicine, Year 1). The free AceMed note covers it in 2 sections, about 606 words (5 min of reading), with 15 flashcards.

In this note

  1. TOPIC 12. Membranous cell organelles. Golgi apparatus, Secretory vesicles, coated vesicles.
  2. Vesicles

TOPIC 12. Membranous cell organelles. Golgi apparatus, Secretory vesicles, coated vesicles.

Golgi apparatus is found in most cells and is another packaging organelle like the ER. The Golgi completes post-translational modifications of proteins synthesised in the RER and then packages and sends the proteins to their proper destinations.

The Golgi has 3 compartments –

  1. 1. Curved stack of flattened cisternae.
  2. 2. Cis face with vesicles.
  3. 3. Trans face/maturing concave face with large condensing vacuoles.
  • Composed of a stack of smooth membranous cisternae containing enzymes for these functions.
  • The Golgi has two faces – a cis face and a trans face.
  • Material from RER cisternae move to SER and are then sent to Golgi in vesicles to the cis face.

The vesicles merge with the cis face. Here the products are checked over. Any goods that have been wrongly delivered, including chemicals that should have stayed in the RER are sent back packed in vesicles to the RER.

  • Correctly delivered proteins and lipids are passed into the cisternae and are processed and sorted according to the labels they bear.
  • On the opposite trans face, large vacuoles accumulate, condense and generate other vesicles that carry completed products of PTM to destinations away from the Golgi.

The destination is linked to the function of the protein products.

  • There are 3 main destinations for the secretory vesicles released from the trans Golgi network:
  1. 1. Inside the cell to the lysosomes
  2. 2. The plasma membrane
  3. 3. Outside of the cell

Enzymes of Golgi apparatus are important for glycosylation, sulfation, phosphorylation and limited proteolysis of proteins.

Along with these activities, the Golgi apparatus initiates packaging and storage of secretory products

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