Role of ER, Golgi & Ribosome in Protein synthesis


Role of ER, Golgi & Ribosome in Protein synthesis


Sites of Protein Synthesis:

→ Proteins & polypeptides synthesized in rough ER (Embedded ribosomes – Actual synthesis site).

→ Proteins stored, concentrated, processed, packed & sorted out in Golgi Apparatus.

STEPS OF PROTEIN SYNTHESIS:

Membrane vesicles containing newly synthesized protein bud off from rough ER  fuse with Cis end (receiving end)  Proteins stored, concentrated, processed, packed & sorted out in Golgi apparatus  Reaches trans side  Secretory vesicles bud off into cytoplasm  finally exocytosed from cell (trans end is secretory end).

Major functions:

1. Post-translational modification:

  • Golgi apparatus present near rough endoplasmic reticulum.
  • Protein synthesized in rough ER  Proteins moves to Golgi apparatus
  • (Glycosylation occurs in Golgi apparatus – Carbohydrate side chain added to protein forming glycoprotein).
  • This step ensures stability of proteins.

2. SORTING OF PROTEINS:

  • Golgi apparatus adds mannose-6-phosphate to proteins  Moves to lysosomes.

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