Notes on Golgi Apparatus and Related Organelles

Golgi Apparatus

• Key organelle in all cells for packaging, processing, and sorting proteins.

• Composed of stacked, flattened membranous sacs.

• Modifies and packages proteins and lipids from the rough endoplasmic reticulum (RER).

• Functions:

  • Receives proteins from RER

  • Can add lipids or carbohydrates

  • Prepares proteins for their final destination (e.g., integration into cell membrane, secretion, or degradation).

Endomembranous System

• Combination of endoplasmic reticulum and Golgi apparatus.

• Transport vesicles carry proteins from RER to Golgi apparatus.

• Proteins can have modifications such as sugar or phosphate groups added.

• Potential fates of proteins:

  • Exocytosis (export)

  • Integration into the membrane

  • Degradation (lysosomes).

Lysosomes

• Membranous bags containing digestive enzymes (hydrolases).

• Functions:

  • Digest harmful materials (bacteria, viruses, toxins).

  • Break down nonfunctional organelles.

  • Release glucose from glycogen (stimulated by glucagon).

  • Release calcium from bones when blood calcium is low.

  • Auto lysis (self-digestion).

Summary of Organelles

• Smooth Endoplasmic Reticulum: Lipid metabolism.

• Nuclear Envelope: Surrounds nucleus; allows export of messenger RNA.

• Rough Endoplasmic Reticulum: Protein synthesis.

• Transport Vesicles: Carry various molecules.

• Lysosomes: Contain hydrolases for metabolic reactions, auto lysis, and degradation.

• Secretory Vesicles: Involved in exocytosis (active transport).

Plasma Membrane

• Characterized by selective permeability; permits certain substances in and out based on specific proteins/channels.