Nucleolus The nucleolus is a structure within the nucleus where the ribosomal subunits are produced. In cells that have been stained, it appears darker than the nucleus. Endoplasmic Reticulum The endoplasmic reticulum is a membranous network that extends throughout the cell. It is continuous with the nuclear envelope and the plasma membrane. Rough Endoplasmic Reticulum The rough appearance of rough endoplasmic reticulum is due to the presence of ribosomes on the membrane. The rough ER functions in protein synthesis , especially proteins that are to be secreted to outside the cell (example: hormones). Proteins enter the lumen (interior) of the endoplasmic reticulum while being synthesized. In addition to protein synthesis, the rough endoplasmic reticulum also functions in the modification of newly formed proteins. For example, some enzymes may add carbohydrate chains forming glycoproteins. Molecular chaperones are enzymes that function to fold the newly-synthesized proteins into their proper shape. Vesicles
This is the end of the preview.
access the rest of the document.