Main Parts of Cells
The Nucleus
The nuclear envelope is a double-walled membrane that separates the nucleus from another part of the cell, the cytoplasm. Like the cell membrane, it is also semipermeable, allowing selected molecules to pass in and out of the nucleus through nuclear pores.
Under a microscope, the nucleolus looks like a dark and round spot in the cell. It has minute fibers and granules. It produces the ribosomes, or important parts of the cell that make the proteins for the organism’s body. The ribosomes do this by linking amino acids into long chains. The nucleoplasm is the jellylike fluid in which the components of the nucleus float. The chromatin is the organized structure that contains the DNA and that forms the chromosomes, or the carriers of hereditary traits, during cell division.
