Cell organelles each have a specific function in order for the cell to be able to carry out its life activities. They are present in Eukaryotic cells. The nucleus contains the hereditary information in the form of chromosomes, which directs the production of proteins in the cell. The nucleolus manufacturers the ribosomal RNA. The cell membrane is selectively permeable and allows the passage of certain materials in or out of a cell. The cytoplasm is the liquid between the membrane and the nucleus, composed of mainly water, where the organelles may be found. Vacuoles are for storage and digestion. Lysosomes contain enzymes which can be used to break down old, worn out cells. Golgi apparatus packages cell secretions and makes them ready to be delivered outside or inside the cell. Endoplasmic reticulum are tubules for intracellular transport. Proteins are folded here. Ribosomes manufacture proteins according to the messenger RNA instructions, copied from the DNA. Mitochondria, are organelles where cellular respiration occurs resulting in the production of A.T.P. which is used by the cell for its energy. If this is an animal cell, centrioles are present which aid a cell during cell division, in the formation of a spindle. If this is a plant cell, there will be a cell wall, outside of the cell membrane, for protection and for support. There will be chloroplasts which contain chlorophyll, a photosynthetic pigment which allow radiant energy to be absorbed and photosynthesis to occur, resulting in the production of glucose. All of these and other organelles are essential for the cell to properly function.