Question

Ribophorin I and II occur on the surface of
A. Rough E.R.
B. Smooth E.R.
C. Golgi body
D. None of the above

Answer 1

Hint:- There are different kinds of glycoproteins or ribosome receptor proteins that are not present in the smooth endoplasmic reticulum membrane but are found in the membrane of the rough endoplasmic reticulum. These glycoproteins have good preservation, great abundance, and importance in the reticulum.

Complete Answer:-
A. Rough E.R. i.e. rough endoplasmic reticulum which is an organelle found in the eukaryotic cells which are made up of cisternae which are involved in the modification of the protein, vesicles, and tubules. RER (Rough Endoplasmic Reticulum) contains ribosomes on its outer surface. Ribophorins are transmembrane glycoproteins or ribosome receptor proteins that are dome-shaped and situated on the rough endoplasmic reticulum. These are classified into two types i.e. Ribophorin I and Ribophorin II and they are only found in the eukaryotic cells.
B. Smooth E.R. i.e. smooth endoplasmic reticulum is a membranous organelle and present in the eukaryotic cells. SER (Smooth Endoplasmic Reticulum) lacks ribosomes on its outer surface. Its primary function is the synthesis of fats, lipids, and carbohydrates and as well as the metabolism of exogenous substances like toxins or drugs. Ribophorin is not present on the smooth endoplasmic reticulum surface.
C. Golgi body is also known as Golgi complex or Golgi apparatus is a membrane-bound organelle present in the eukaryotic cells having clearly defined nuclei. It is situated in the cytoplasm next to the endoplasmic reticulum and near the nucleus of the cell. Its main function is to process and pack proteins and lipid molecules and is involved in the secretion and intracellular transport.
D. None of the above.

As we have discussed above the correct option is A (Rough E.R.).

Note:- Ribophorin helps in the binding of the 60S subunit of the eukaryotic ribosome to bind to the rough endoplasmic reticulum. They play a vital role in the co-translational translocation methods.