Why does the chloroplast have a double membrane?

Chloroplasts contain several important membranes, vital for their function. Like mitochondria, chloroplasts have a double-membrane envelope, called the chloroplast envelope, but unlike mitochondria, chloroplasts also have internal membrane structures called thylakoids. read more

The bottom line is that nobody currently knows why chloroplasts need a double membrane. Nicole’s answer is correct in as far as it goes: chloroplasts are descended from cyanobacteria, and the inner chloroplast membrane lipid composition reflects that of cyanobacteria, while the composition of the outer membrane reflects that of eukaryotes. read more

Like mitochondria, chloroplasts have a double-membrane envelope, called the chloroplast envelope, but unlike mitochondria, chloroplasts also have internal membrane structures called thylakoids. Furthermore, one or two additional membranes may enclose chloroplasts in organisms that underwent secondary endosymbiosis, such as the euglenids and chlorarachniophytes. read more