Endoplasmic Reticulum (Rough and Smooth)
what is the smooth ER
In liver cells for example smooth ER enables glycogen that is stored as granules on the external surface of smooth ER to be broken down to glucose.
what are the proteins that are produced for?
Proteins are produced for the plasma membrane, Golgi apparatus, secretory vesicles, plant vacuoles, lysosomes, endosomes and the endoplasmic reticulum itself.
what does the Ribosomes on the rough endoplasmic reticulum do and what are they called?
Ribosomes on the rough endoplasmic reticulum are called 'membrane bound' and are responsible for the assembly of many proteins. This process is called translation.
ROUGH ENDOPLASMIC RETICULUM
This is an extensive organelle composed of a greatly convoluted but flattish sealed sac that is continuous with the nuclear membrane. It is called 'rough' endoplasmic reticulum because it is studded on its outer surface (the surface in contact with the cytosol) with ribosomes. These are called membrane bound ribosomes and are firmly attached to the outer cytosolic side of the ER About 13 million ribosomes are present on the RER in the average liver cell. Rough ER is found throughout the cell but the density is higher near the nucleus and the Golgi apparatus.
what does the Smooth ER do?
Smooth ER is devoted almost exclusively to the manufacture of lipids and in some cases to the metabolism of them and associated products. Smooth ER is also involved in the production of steroid hormones in the adrenal cortex and endocrine glands.
SMOOTH ENDOPLASMIC RETICULUM
Smooth ER is more tubular than rough ER and forms a separate sealed interconnecting network. It is found fairly evenly distributed throughout the cytoplasm. It is not studded with ribosomes hence 'smooth ER'.
what does the rough ER workig with the membrane bound ribosomes do?
The rough ER working with membrane bound ribosomes takes polypeptides and amino acids from the cytosol and continues protein assembly including, at an early stage, recognising a 'destination label' attached to each of them.