The Endoplasmic Reticulum, Ribosomes, and Protein Synthesis

For many years, the cytoplasm of the living cell was conceived of as a rather homogeneous gel in which particles such as the plastids and the mitochondria were suspended. The electron microscope revealed the existence of additional structures in the cytoplasm and clearly established the complex nature of the cytoplasm. Among the first structures observed with the electron microscope were the endoplasmic reticulum , or ER, and the ribosomes .