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).
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.