Question

Studies of the endomembrane system often involve the use of a protein that can emit a green fluorescence (glow). A researcher wants to make a video of cell behavior, so she initially labels the outer nuclear envelope of a cell with the fluorescent tag and records a video for several hours. Later, she sees that the tag is part of a transport vesicle very close to the plasma membrane.
The fluorescent tag likely did not become incorporated into which of the following organelles?

Answer 1

Answer:

The correct answers are: Ribosome, Mitochondria, Chloroplast (in case of a plant cell).

Explanation:

• The Endo-membrane system in the cell represents the membranes of the Nucleus, Endoplasmic Reticulum, Golgi apparatus, Plasma Membrane, Vacuole and Lysosome.
• The Nuclear Envelope is made up of a phospholipid bilayer which remains in continuation with the ER (endoplasmic reticulum) membrane.
• Therefore, fluorescent tagged integral membrane protein localised in the outer nuclear envelope can move into the ER membrane by lateral movement or through vesicles that bud off from the membrane of the nuclear envelope and fuse with that of the ER membrane.
• Vesicles bud off from the membrane of the ER and fuse with the Golgi apparatus. Therefore, the fluorescent tagged integral membrane protein can move into the membrane of the Golgi apparatus.
• Vesicles bud off from the Golgi apparatus and fuse with the Plasma membrane, Lysosome membrane, and Vacuole membrane. Hence, the fluorescent tagged integral membrane protein can be found in all these organelles.
• Ribosome lacks a membrane and hence, the fluorescent tagged integral membrane protein will be absent over here.
• Both Mitochondria and Chloroplast, are self-replicating and dividing organelles. Their proteins (membrane or matrix) are encoded mostly by their own genome. Also, vesicles that bud from from nucleus or ER or Golgi apparatus do not fuse into their membrane. Hence, the fluorescent tagged protein would not be able to reach their membrane.