Mitochondrion and chloroplast have a double membrane. Its origin is explained by the endosymbiont theory. A nucleus has never ended up in another cell as a ‘foreign’ organism; the nuclear membrane was created to protect the DNA. Why is a single membrane not sufficient here? How and why did the second originate?
Answer
Best,
The double nuclear membrane is formed by the endoplasmic reticulum: these flattened membrane sacs lie around the nuclear material after nuclear division, merge into two continuous membranes, closed all around, in which nuclear pores are placed. The ribosomes on the ER continue to work (yet on the cytoplasmic side). The nuclear membrane, or rather the nuclear membranes with intermembrane solution in between, are part of the ER: an organelle in itself, with function as a normal ER, but additionally controlling entry and exit via nuclear pores.
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Answered by
ir. Myriam Meyers
industrial microbiology and biochemistry
Old Market 13 3000 Leuven
https://www.kuleuven.be/
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