Endoplasmic Reticulum (ER)

General ER Structure

• "the network within"
• Internal space separate from cytosol.
• Contiguous with the inside of nuclear membrane!
• Two distinct connected regions (smooth and rough ER).

Smooth ER

• Arranged as "pipes".
• Functions:
  • Synthesis of lipids and carbohydrates.
  • Detoxify drugs (liver).
  • Secrete steroids (sex hormones).

Rough ER

• Arranged as flattened, stacked sacs.
• Dotted with ribosomes. Ribosomes can become detached.
• Functions:
  • Assemble of polypeptides.
  • Makes more membranes.
  • Polypeptides can be kept inside ER and "budded" off into transport vesicles.