Why does the Rough Endoplasmic Reticulum look 'rough' under a microscope?

The correct answer is Due to the presence of ribosomes on its surface.

Key Points

• The Rough Endoplasmic Reticulum (RER) appears "rough" under a microscope because it is studded with ribosomes on its cytoplasmic surface.
• Ribosomes are responsible for protein synthesis, which is one of the primary functions of the RER.
• The association of ribosomes with the RER gives it a granular or rough appearance when viewed under an electron microscope.
• The RER is particularly abundant in cells that are actively involved in protein secretion, such as pancreatic cells and plasma cells.
• These ribosomes synthesize proteins that are either secreted from the cell, incorporated into the plasma membrane, or used within lysosomes.

Additional Information

• Endoplasmic Reticulum (ER):
  • The ER is an extensive network of membranes found in eukaryotic cells, divided into two types: Rough ER (RER) and Smooth ER (SER).
  • The RER is involved in protein synthesis and modification, while the SER is involved in lipid synthesis and detoxification processes.
• Ribosomes:
  • Ribosomes are small organelles composed of RNA and proteins, responsible for assembling polypeptides during protein synthesis.
  • They can be free-floating in the cytoplasm or attached to the RER.
• Protein Secretion Pathway:
  • Proteins synthesized on the RER are transported to the Golgi apparatus for modification and packaging.
  • They are then sent to their final destinations: secretion, plasma membrane insertion, or lysosome incorporation.
• Electron Microscopy:
  • The granular appearance of the RER was first observed using electron microscopes, which provide detailed cellular images.
  • This technique allows scientists to study the ultrastructure of organelles like the RER and ribosomes.