Endoplasmic Reticulum (ER)

i. Endoplasmic reticulum is a network present within the cytosol.

ii. It is present in all eukaryotic cells except ova (female reproductive cell/egg cell)  and mature red blood corpuscles.

iii. Under the electron microscope, it appears like network of membranous tubules (ERs) and sacs called cisternae.

iv. This network of ER divides the cytoplasm in two parts viz. one within the lumen of ER called laminal cytoplasm and non-laminal cytoplasm that lies outside ER.

v. Membrane of ER is continuous with nuclear envelope at one end and extends till cell membrane. It thus acts as intracellular supporting framework and helps in maintaining position of various cell organelles in the cytoplasm.

vi. Depending upon the presence or absence of ribosomes, endoplasmic reticulum is called rough endoplasmic reticulum (RER) or smooth endoplasmic reticulum (SER) respectively.

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