By Catherine Beyer. The ankh is the most well known symbol to come out of ancient Egypt. In their hieroglyphic system of writing the ankh represents the concept of eternal life, and that is the general meaning of the symbol. Construction of the Image:
The outer layer of the double membrane is much more permeable than the inner layer, which features a number of embedded membrane transport proteins. Enclosed by the chloroplast membrane is the stroma, a semi-fluid material that contains dissolved enzymes and comprises most of the chloroplast's volume. Since, like mitochondria, chloroplasts possess their own genomes (DNA), the stroma contains chloroplast DNA and special ribosomes and RNAs as well.
Mitochondria and Chloroplast carry some genetic information necessary for their function. The ribosomes are equivalent to Prokaryotic 70S ribosomes, and nyclear DNA encodes some of the component that makes up these ribosomes. Also, Mitochondria and Chloroplast have double membrane that surrounds these organelle. No one knows for sure. One hypothesis is that a long, long time ago a cell endocytosed a prokaryotic cell and these two cells formed a symbiotic relationship. The inner cell (mitochondria and chloroplasts) was protected from the environment and the outer cell received energy.