Question

1. Describe how proteins are targeted and synthesized in the ER.

2. Describe nuclear pore transport. Why a pore and not a simple membrane translocator?

3. Describe how exocytose and endocytose vesicle targeting mechanisms.

Answer 1

mRNA Ribosome SRP replaced and recycled SRP S signal cytosol recognition ER signal particle) SRP receptor in Er membrane Translocation channel sequence on growing polypeptid chain Ribosome with mRNA having polypeptice chain with ER signal sig sequence and the SRP (signal recognition particle moves to ER(endoplasmic reticulum) and binds to SRP receptor that is present in the ER membrane. Then it moves on and clock with translocation channel and releases SRP and protein sis continues. nucleus 2 . < basket innex membrane -nuclear ring nuclear envelope outer membrane cytoplasmic ring control Framework cytoplasmic fibrils cytoplasm This is the structure of nuclear pore complex. This allows transport of molecules such as RNA, proteins et across the nuclear envelope. There is transport in lout of nucleus. Nuclear envelope is needed for transport. There will be a signal and

receptor for carrying the molecules insout. Here transport is only done by nuclear pore. Also macro- molecules can only be transported through pores. 3. In endocytosis, The material is taken in. it outside materials - 0 lipid bilayer lysosome The molecules present outside is taken in by lysosome by engulfing by the rescicle. Two types are there- o phagocytosis ③ pinocytosis. In exocytosis, the materials are moving out of the cell or vescicle. lipid bilayer The molecules / materials present in the reseacle is moved out of the cell through the process, enclocytosis exocytosis. That is the materials are expelled out