Organelles are the specialized parts of the cell that have unique jobs to perform. Let’s start with the nucleus, the control center of the cell. The nucleus contains DNA, or genetic material. The nucleus also contains a nucleolus, which is a structure where ribosomes are made. Ribosomes may wonder freely within the cytoplasm, or attach to the endoplasmic reticulum, sometimes abbreviated as E.R. Proteins and other materials emerge from the endoplasmic reticulum in small vesicles where the Golgi apparatus, sometimes called the Golgi body, receives them. The Mitochondrion is an organelle that is the power house for both animal and plant cells. During a process called cellular respiration the Mitochondria make ATP molecules that provide the energy for all of the cell’s activities.