Organelles and protein trafficking
Ribosomes translate mRNA. Ribosomes associated with rough ER feed certain new polypeptides into the ER or its membrane; free ribosomes usually produce proteins that remain in the cytosol or are targeted to some other locations. The ER helps fold and process proteins and contributes to membrane production. The Golgi modifies and sorts cargo into vesicles. Lysosomes digest selected cargo, while vacuoles contribute to storage and water balance. Mitochondria support aerobic energy metabolism; chloroplasts perform photosynthesis in photosynthetic eukaryotes. Organelles work as a coordinated system, so failure of one trafficking step can redistribute cargo without stopping all translation.
If ER-to-Golgi transport is blocked in a gland cell, secretory protein can accumulate in the ER while secretion falls. This does not mean the Golgi normally reads the mRNA or that every cytosolic protein stops being made.
Ribosomes, not the Golgi, join amino acids into the primary polypeptide sequence. Plants also have mitochondria; chloroplasts do not replace respiration.