* Cisternae: These are the flattened, membrane-bound sacs that give the ER its characteristic network structure.
* Ribosomes: These appear as small, dark granules attached to the outer surface of the cisternae. The ribosomes are what give the RER its "rough" appearance.
* Overall Appearance: The RER appears as a network of interconnected, flattened sacs with numerous dark granules attached to their surface.
Here's a more detailed explanation:
* Light Microscopy: Under a light microscope, the RER appears as a network of interconnected, thin, dark lines or bands. The ribosomes are too small to be seen individually, but their presence gives the RER a granular appearance.
* Electron Microscopy: Under a transmission electron microscope (TEM), the RER's structure is much more detailed. The cisternae appear as flattened, membrane-bound sacs with a distinct lumen (internal space). The ribosomes are clearly visible as dark granules attached to the outer surface of the cisternae.
Key features to look for:
* Interconnected network: The RER is a continuous network, not isolated sacs.
* Flattened sacs: The cisternae are flattened and not spherical like other organelles.
* Ribosome density: The density of ribosomes attached to the RER can vary depending on the cell type and its activity.
Remember: The appearance of the RER can vary depending on the type of microscope used, the preparation of the sample, and the specific cell type being observed.
