Question

R.E.R is specialised for the synthesis of
A) Local proteins
B) Local proenzymes
C) Proteins and proenzymes for transport
D) Hormones

Answer 1

Hint: R.E.R stands for rough endoplasmic reticulum. It is rough due to the presence of ribosomes.

Complete Answer:
- Endoplasmic reticulum is one of the most important organelle of a eukaryotic cell. It forms an interconnected network of membrane enclosed sacs called the cisternae and tubular structures. The endoplasmic reticulum transports the glycoprotein throughout the cell.
- There are two types of Endoplasmic reticulum. Different types of cells have different types of endoplasmic reticulum composition depending on the function of the cell.
1) Smooth endoplasmic reticulum (S.E.R)- This area in ER does not contain ribosomes. The Smooth ER synthesises lipids, phospholipids and steroids. The cells which need these molecules have abundant S.E.R like ovaries, sebaceous glands.
2) Rough Endoplasmic reticulum R.E.R- It is also called a granular Endoplasmic reticulum. They have the protein manufacturing unit called the ribosome which gives it a rough appearance.
- The membrane of R.E.R occurs continuously with the nuclear membrane. The main function of Rough Endoplasmic Reticulum is manufacture of lysosomal enzymes, manufacture of secreted proteins, and synthesis of integral membrane proteins. They manufacture protein and transport it to other parts of the cells.

Thus the correct answer is (C). R.E.R synthesises protein and proenzymes for transport.

Note: E.R is an important centre for protein synthesis due to the presence of ribosomes. They transport proteins to different parts of the body.