STPM Biology Structure of Cell and Organelle (Part 5)

Endoplasmic reticulum

Distribution:

• Rough endoplasmic reticulum (RER) are usually attached to the nucleus. Smooth endoplasmic reticulum (SER) are dispersed in the cytoplasm.
• Found in abundance in liver cells (detoxification center), pancreatic cells (secretes enzymes) and brain cells.

  

  RER, SER and Ribosomes
  

Structure:

• Endoplasmic reticulum is a network of flattened sacs and tubules. Endoplasmic reticulum is surrounded by a membrane.
• Rough endoplasmic reticulum (RER) is the network of flattened sacs bounded by a membrane. Robosomes are found on the surface of RER.
• Smooth endoplasmic reticulum (SER) is a network of tubules. No ribosomes are present.
• Endoplasmic reticulum is filled with fluid. This fluid contains carbohydrates, protein, lipids, cholesterols and steroids.

Functions:

• Smooth endoplasmic retiulum (SER) synthesizes, secretes and stores lipid, steroids, choloesterols and carbohydrates.
• SER is a main site for detoxification substances in cells, especially liver cells. Enzymes in SER catalyze the break down of a variety of poisons and toxic compounds.
• Ribosomes on the rough endoplasmic reticulum (RER) manufacture proteins and enzymes.
• Both endoplasmic reticulum also serve as an intracellular transport system.