How are the golgi apparatus and endoplasmic reticulum related?
They are both components of the Endomembrane system, and in combination the ER and Golgi are responsible for anterograde and retrograde transport of proteins.
Anterograde transport: The Rough ER is a site for protein synthesis(mRNA->protein), as performed by ribosomes that are attached to the surface. Many of these synthesized peptides contain sequences that determine their destination. Some are packaged into vesicles that fuse to form the cis-Golgi cisternae.
The cargo of these vesicles can have multiple destinations. They may be secretory proteins, Transmembrane proteins or they may be packaged into Lysosomes.
Retrograde transport: Proteins from outside that are destined for the ER are packaged into golgi vesicles that fuse with the ER.
Keywords to read more on:
Translocon, Sec61, TRAM.
Signal recognition peptides (SRP)
COP1 and COP2, Clathrin coated vesicles and Lysosomal targeting
Glycosylation in the ER
Alberts Molecular Biology of the Cell, 5th edition, chapter 11.