The correct answer is ribosomes. Key Points - The cell has three main parts: - The cell membrane - Cytoplasm, which contains smaller components called organelles - The nucleus - The nucleus is separated from the cytoplasm by a membrane called the nuclear membrane. - This membrane is also porous and allows the movement of materials between the cytoplasm and the inside of the nucleus. - The movement of materials to different parts of the cytoplasm and nucleus is generally carried out by ribosomes.