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BioFlix: Endomembrane System

by Pearson
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Protein processing and certain other metabolic activities occur in the endomembrane system, the cell's network of internal membranes. The endoplasmic reticulum, or ER, is part of the endomembrane system. There are two types of ER, rough and smooth. Rough ER is covered with ribosomes. Smooth ER lacks ribosomes. Lipids are made in the smooth ER. Let's go inside the rough ER. Note that you can still see the ribosome on the outside surface. The ribosome is manufacturing a new protein, which continues to grow inside the ER. Completed proteins move to the edge of the rough ER and depart in a vesicle that buds off from the ER membrane. Some vesicles fuse with the Golgi apparatus, another component of the endomembrane system. In the Golgi, proteins undergo further processing. Finished proteins are then packaged in vesicles that pinch off from the Golgi and are transported along cytoskeleton tracks. Some vesicles bind with the plasma membrane, secreting their contents outside the cell. Other vesicles, called lysosomes, contain digestive enzymes. Here, a lysosome fuses with a worn out mitochondrion and breaks it down.
Protein processing and certain other metabolic activities occur in the endomembrane system, the cell's network of internal membranes. The endoplasmic reticulum, or ER, is part of the endomembrane system. There are two types of ER, rough and smooth. Rough ER is covered with ribosomes. Smooth ER lacks ribosomes. Lipids are made in the smooth ER. Let's go inside the rough ER. Note that you can still see the ribosome on the outside surface. The ribosome is manufacturing a new protein, which continues to grow inside the ER. Completed proteins move to the edge of the rough ER and depart in a vesicle that buds off from the ER membrane. Some vesicles fuse with the Golgi apparatus, another component of the endomembrane system. In the Golgi, proteins undergo further processing. Finished proteins are then packaged in vesicles that pinch off from the Golgi and are transported along cytoskeleton tracks. Some vesicles bind with the plasma membrane, secreting their contents outside the cell. Other vesicles, called lysosomes, contain digestive enzymes. Here, a lysosome fuses with a worn out mitochondrion and breaks it down.