Question

What is more abundant in R.E.R?
A. Cisternae
B. Vesicles
C. Tubules
D. Both A and B

Answer 1

These are the flattened membrane discs found in endoplasmic reticulum and Golgi apparatus. A Golgi stack can contain three to twenty disks of this organelle.

Complete answer:
The endoplasmic reticulum (ER) is a large network of membrane-bound tubes and sheets. It looks like long tubes or oval or oblong bags (vesicles). The membrane of ER is similar in structure to that of the plasma membrane. The ER is a type of organelle consisting of two subunits - the smooth endoplasmic reticulum (SER) and the rough endoplasmic reticulum (RER). ER is present in most eukaryotic cells and develops an integrated network of flattened, membrane-enclosed sacs defined as cisternae in the RER and tubular structures in the SER.
RER is arranged in smooth cistern aggregates that can be contained in the cytoplasm. It is more widely distributed in perinuclear, pericanalicular, and sub basilar hepatocyte areas, and is more concentrated in periportal cells than in centrilobular cells. The various ribosomes attached to the membrane consist of a small and a large subunit. The large subunits of proteins are attached to the RER. Free ribosomes and polyribosomes are also found in the hepatocyte cytoplasm. Ribosomes contain ribosomal proteins and RNA and play an important role in protein synthesis, especially those intended for secretion or delivery to intracellular membrane compartments or to the plasma membrane. Vesicles containing these proteins are led to the nearby Golgi cistern for further processing.

Thus, the correct answer is option A i.e., Cisternae.

Note: RER appears rough under a microscope since it has particles called ribosomes bound to the surface. Ribosomes, which are found in all active cells, are the places of protein synthesis.